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    Asian J Androl 2008; 10 (3): 351-363

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- Review -

The physiological and pharmacological basis for the ergogenic effects of androgens in elite sports

Karen Choong, Kishore M. Lakshman, Shalender Bhasin

Boston University School of Medicine, Section of Endocrinology, Diabetes, and Nutrition, Boston Medical Center, Boston, MA 02118, USA

Abstract

Androgen doping in power sports is undeniably rampant worldwide. There is strong evidence that androgen administration in men increases skeletal muscle mass, maximal voluntary strength and muscle power. However, we do not have good experimental evidence to support the presumption that androgen administration improves physical function or athletic performance. Androgens do not increase specific force or whole body endurance measures. The anabolic effects of testosterone on the skeletal muscle are mediated through androgen receptor signaling. Testosterone promotes myogenic differentiation of multipotent mesenchymal stem cells and inhibits their differentiation into the adipogenic lineage. Testosterone binding to androgen receptor induces a conformational change in androgen receptor protein, causing it to associate with beta-catenin and TCF-4 and activate downstream Wnt target genes thus promoting myogenic differentiation. The adverse effects of androgens among athletes and recreational bodybuilders are under reported and include acne, deleterious changes in the cardiovascular risk factors, including a marked decrease in plasma high-density lipoproteins (HDL) cholesterol level, suppression of spermatogenesis resulting in infertility, increase in liver enzymes, hepatic neoplasms, mood and behavioral disturbances, and long term suppression of the endogenous hypothalamic-pituitary-gonadal axis. Androgens are often used in combination with other drugs which may have serious adverse events of their own. In spite of effective methods for detecting androgen doping, the policies for screening of athletes are highly variable in different countries and organizations and even existing policies are not uniformly enforced. (Asian J Androl 2008 May; 10: 351_363)

Keywords: testosterone; dihydrotestosterone; muscle mass; mechanisms of androgen action; androgen doping; mesenchymal stem cells; detection of androgen doping

Correspondence to: Prof. Shalender Bhasin, Boston University School of Medicine, Section of Endocrinology, Diabetes, and Nutrition, Boston Medical Center, Boston, MA 02118, USA.
Tel: +1-617-414-2951 Fax: +1-617-638-8217
E-mail: Shalender.Bhasin@bmc.org
Received 2008-01-02 Accepted 2008-01-08

DOI: 10.1111/j.1745-7262.2008.00407.x


1 Introduction

George J. Mitchell, a former US Senator, in a recent report on the use of illegal performance-enhancing drugs in professional baseball, acknowledged pervasive use of androgenic-anabolic steroids by Major League Baseball players in the USA; the list of those linked to steroid use included many well known names in baseball. The keen observers of the professional sports scene, who have been sounding the alarm over the widespread use of ergogenic drugs worldwide—not just in the USA, and in all professional sports—not just baseball—for the past two decade, were hardly surprised by these revelations. The use of performance enhancing agents in sports is not a new phenomenon; documentation exists of the use of a variety of potions, plants, animal extracts as far back as the original Olympiads in ancient Greece. Long before the isolation and synthesis of testosterone in the 1930s, Brown-Sequard and later Zoth and Pregl had recognized that contents of the testicular extracts could improve physical and mental energy, and muscle strength [1_4]. Shortly after successful synthesis of testosterone, Boje [5] suggested that sex hormones might enhance physical performance. The Germans are alleged to have administered anabolic -androgenic steroids to soldiers going into combat [6]. Although it has been alleged that some German athletes were given testosterone in preparation for the 1936 Berlin Olympics [6], the most cited account of systematic use of androgens in elite sports is that of the Soviet weight lifting team in the 1952 and 1956 Olympics. In 1954, at the weight lifting championships in Vienna, Dr John Ziegler, a physician associated with the US Weight Lifting Team, learned about the use of androgens by the Russian weight lifters [6, 7]. Zeigler returned to the United States and experimented with testosterone on himself and other weight lifters in the York Babel Club [7]. When Ciba Pharmaceuticals introduced Dianabol (methandrostenolone) in 1958, he began to experiment with this new drug [6, 7]. The use of androgens that was limited initially to strength-intensive sports, spread gradually over the ensuing decades to other sports and to recreational body building [6, 7]. The media lime light surrounding the detection of androgen use by elite athletes such as Ben Johnson, Lyle Alzado, Mark Maguire, Barry Bonds, Floyd Landis, and Marion Jones has only added to the allure of performance enhancing drugs.

Admittedly, the exact prevalence of androgens use by athletes is difficult to determine because the data rely on self-reports and many users understandably do not admit to the use of these drugs. But even surveys based on self-report have found high rates of androgens use among professional athletes and Olympians [7, 8]. Yesalis estimated that approximately one million Americans had used androgens sometime in their lives [9]. Four to six percent of high school boys and one to two percent of high school girls admit to using androgens at least once [10_13]. The androgen use among girls also has increased slightly during the past decade although the overall use rates are substantially lower in women than in men [7, 10].

The abuse of performance-enhancing drugs is not limited to the USA; similar high prevalence rates of androgen use have been reported in surveys conducted in other countries [14, 15]. The most egregious example of state-sponsored anabolic steroid doping was uncovered in the former German Democratic Republic after the fall of the communist government in 1990 [16]; classified documents revealed a secret state program from 1966 to improve national athletic performance using androgens with complicity of the sports medicine physicians.

A recent study of the use of anabolic steroids among US college students found that the overall prevalence of androgen use was 1% or less [17]. The number of students reporting past-year use of androgens increased among men from 1993 (0.36%) to 2001 (0.90%) [17] and has decreased slightly since then [18]. The lifetime and past-year steroid use were associated with being male, participation in intercollegiate athletics, and risky behaviors, including cigarette smoking, illicit drug use, drinking and driving, and alcohol use disorders [17]. One of the most alarming finding of this survey was that approximately 70% of lifetime users of anabolic steroids met criteria for an alcohol use disorder [17]. Thus, college athletes who abuse androgens are at increased risk for other risky health behaviors.

2 Patterns of androgen abuse by athletes and recreational body builders

Nandrolone, testosterone, stanozolol, methandienone, and methenolol are the most frequently abused androgens [19_21]. Intramuscular formulations of androgens are used far more frequently than oral formulations [19]. Combinations of androgens are used more frequently than single agents [19, 21]. Typically, athletes use two or more androgens in progressively increasing doses over a period of several weeks in a practice known as "stacking". The doses of testosterone or other androgens used by athletes are substantially larger than those prescribed for the treatment of androgen deficiency. In one survey [19], 50% of androgen users reported using at least 500 mg of testosterone weekly or an equivalent dose of another androgen; in another survey [21], almost one fourth of androgen users used 1 000 mg testosterone weekly or an equivalent dose of other androgens. Cycling of androgens refers to the intermittent use of androgens in which weeks of androgen use are followed by periods of drug holiday; this practice is based on the unproven premise that cyclic prevents desensitization to massive doses of androgen.

In addition to the use of androgens, athletes also abuse other drugs to purportedly enhance muscle-building, muscle shaping, or athletic performance [19]. These accessory drugs include stimulants, such as amphetamine, clenbuterol, ephedrine, and thyroxine, other anabolic agents such as growth hormone, IGF-1, and insulin, and drugs perceived to reduce adverse effects such as hCG, aromatase inhibitors or estrogen antagonists [19]. The potential adverse effects of some accessory drugs may be more serious than those of androgens.

3 Do androgens improve athletic performance?

Surprising as it might seem in light of the widespread abuse of androgens, the evidence demonstra-ting improvements in athletic performance after androgen administration is sparse and weak. There is strong evidence that androgens increase skeletal muscle mass, maximal voluntary strength, and leg power [22_27]; even this assertion was debated rancorously for almost five decades. Much of the controversy stemmed from the well recognized difficulties in conducting placebo-controlled, randomized, masked trials in athletes [27, 28]. It is not surprising that many of the earlier androgen trials were neither randomized nor blinded. Some studies included competitive athletes whose adherence to rigid research protocols is always suspect [27, 28]. The protein and energy intake was not standardized; in some studies, the participants continued to ingest protein supplements ad lib. The exercise stimulus was not standardized and, therefore, the effects of resistance exercise could not be separated from those of androgen administration.

However, a growing body of data over the past decade has established that androgens increase muscle mass [25, 26] and that the androgen-induced gains in skeletal muscle mass and muscle strength are correlated with the administered dose and the circulating concentrations (Figure 1) [23, 24, 29, 30]. Thus, administration of replacement doses of testosterone to healthy, hypogonadal men [31_35] and of supraphysiologic doses to eugonadal men [22, 23] increases lean body mass, muscle size and strength (Figure 2). Systematic reviews of randomized clinical trials have confirmed that testosterone therapy is associated with greater gains in lean body mass and grip strength than placebo in older men with low or low normal testosterone levels [25]. Similarly, testosterone therapy in HIV-infected men with weight loss and in men with chronic obstructive lung disease promotes greater gains in lean body mass and muscle strength than placebo. There is considerable inter-subject variability in the anabolic response to androgen administration. A large part of the variance in anabolic response can be explained by the circulating androgen concentrations; however, polymorphisms in the polyglutamine and polyglycine tract length in androgen receptor protein, testosterone metabolism, and other unknown genetic factors may contribute to this variance [30].

The effects of testosterone on muscle performance are domain specific; testosterone administration improves muscle strength and power, but does not affect specific force or muscle fatigability. The gains in maximal voluntary strength during testosterone administration are highly correlated with increments in muscle mass; testosterone does not improve the contractile property of the skeletal muscle. In contrast, resistance exercise training increases muscle mass as well as specific force. Androgens have not been shown to improve measures of whole body endurance, such as VO2max and lactate threshold.

Based on their demonstrable effects on maximal voluntary muscle strength, androgens would be expected to improve performance in events such as power lifting in which performance is dependent upon muscle strength. Therefore, not surprisingly, high rates of androgen use have been reported among power lifters. Body builders use androgens to increase skeletal muscle mass and decrease fat mass, which provides greater definition to the muscles. However, the use of androgens by athletes participating in endurance events such as long distance running and bicycling is not easily comprehensible because androgens have not been shown to improve endurance measures [36, 37]. It is possible that the androgen-induced increments in hemoglobin may improve the oxygen carrying capacity of blood [38]. The speculation that androgens might allow the athletes to train harder by improving the regenerative response of the skeletal muscle to injury has not been tested rigorously. Others have suggested that androgens might increase "motivation" and "aggression", which may be advantageous in competitive sports.

The widespread use of androgens by baseball players and sprint runners also is not easily explained by the available data on the effects of androgens. The ability to hit a home run against a ball traveling at speeds approaching 100 mph requires extraordinary degree of hand-eye coordination—the ability to locate the ball in a specific coordinate of space and to place the bat in that precise coordinate with considerable strength and power. There is some evidence that androgens decrease reaction time by improving neuromuscular transmission [39, 40]. Improved reaction time in conjunction with increased strength and power could potentially explain the perceived improvements in athletic performance by baseball players, although the evidence to support these hypotheses is lacking.

The use of androgens by legendary sprinters like Ben Johnson is even more difficult to explain. Among sprint runners, androgen-induced gains in body weight might potentially increase the amount of work done in carrying that body weight against gravity and resistance across the race track. Thus weight gain might be viewed as potentially deleterious to performance. The improved reaction time, the psychological edge gained because of the motivational effects of androgens, and the ability to train harder, have been cited as possible explanations without verifiable evidence.

4 Mechanisms of anabolic effects of androgens

Testosterone-induced increase in skeletal muscle mass is associated with dose-dependent increase in cross-sectional area of both type I and type II muscle fibers [41]. Testosterone administration does not affect the absolute number or the relative proportion of type I and type II muscle fibers [41]. Testosterone administration increases the numbers of myonuclei and satellite cells [42], muscle progenitor cells that reside in a unique niche adjacent to the muscle fiber. Androgen receptors are expressed in the satellite cells and other stem-like cells in the interstitium of the skeletal muscle fibers and in some myonuclei of the myofibers [43]. A growing body of evidence supports the hypothesis that androgens promote the differentiation of mesenchymal multipotent stem cells into the myogenic lineage and inhibit their differentiation into the adipogenic lineage [44_46]. Thus, in cultures of mesenchymal multipotent C3H10T1/2 cells, androgens upregulate markers of myogenic differentiation, such as MyoD and myosin heavy chain II and downregulate markers of adipogenic differentiation, such as PPAR-gamma and C/EBP-alpha [46]. These effects of testosterone and DHT on myogenesis are mediated through the classical androgen receptor-mediated signaling and are blocked by bicalutamide, an androgen receptor antagonist [46].

Upon binding to its cognate ligand, androgen receptor undergoes conformational change and associates with its co-activator beta-catenin [45]. The androgen receptor-beta catenin complex moves into the nucleus, forms a complex with LEF/TCF-4, and activates a number of Wnt target genes, including follistatin [45]. The signal from androgen receptor is cross-communicated to the TGF-beta pathway through beta-catenin and TCF-4. Beta-catenin and follistatin play an essential role in mediating the effects of testosterone on myogenic differentiation [45].

Testosterone also has been reported to promote satellite cell entry into the cell cycle [47_51]. Additionally, testosterone and DHT inhibit the differentiation of preadipocytes into adipocytes [45]. Androgens also stimulate fractional muscle protein synthesis and to increase the efficiency of reutilization of amino acids by the skeletal muscle [32, 52_54]. The effects of testosterone on muscle protein degradation need further investigation.

5 Potential adverse effects of androgen use

Because of the variability in the dose, frequency, duration, and the type of drugs used, systematic investigations of the adverse effects of androgens in athletes and recreational body builders have been difficult to conduct. These analyses are further complicated by the concurrent use of accessory drugs. The low frequency of serious adverse effects reported with androgen use is surprising; it is likely that the adverse effects are under-reported. Furthermore, the accuracy of self-reported drug use is difficult to verify.

Adverse events associated with androgen use include deleterious changes in the cardiovascular risk factors, including a marked decrease in plasma high-density lipoproteins (HDL) cholesterol level [55] and changes in clotting factors [56], suppression of spermatogenesis resulting in infertility, increase in liver enzymes, hepatic neoplasms, and mood and behavioral disturbances [57_63]. Elevations of liver enzymes, hepatic neoplasms, and peliosis hepatic and even hepatic rupture have been reported with the use of oral, 17-alpha alkylated androgens [57, 58, 64], but not with parenterally administered testosterone or its esters [65]. Acne and premature hair loss can occur with androgen use. Women using large dose of androgens are at risk for menstrual irregularities, infertility, and virilizing side effects, including hirsutism, deepening of voice, changes in body habitus, and clitoral enlargement; some of these virilizing adverse effects may be irreversible.

A number of deaths due to unexpected coronary and cerebrovasuclar thrombotic events among androgen users have been reported [66_68], but these reports are largely anecdotal and do not establish a cause and effect relationship. In a stunning report that has received surprisingly little attention, Finnish world class power lifters suspected of AAS intake during their sports career experienced five times higher mortality than age-matched controls [69]. The findings of this small study need further confirmation. The changes in plasma lipids vary depending on the dose, the route of administration (oral or parenteral), and whether the androgen is aromatizable or not. Thus, orally administered, 17-alpha-alylated, nonaromatizable androgens produce greater reductions in plasma HDL cholesterol levels than parenterally administered testosterone. Orally-administered, 17-alpha alkylated androgens also have been associated with insulin resistance and glucose intolerance [70]. Androgen use has been associated with increases in hematocrit, homocysteine levels, blood pressure and peripheral arterial resistance, and left ventricular hypertrophy and diastolic dysfunction [71_81]. However, it is not clear whether myocardial hypertrophy reported in power lifters is the result of resistance exercise or androgen use. In a cross-sectional investigation [82], power athletes who had used androgens showed subclinical impairment of both systolic and diastolic myocardial function that was correlated with the dosage and duration of androgen use. Also, one controlled trial in healthy volunteers [83] and other uncontrolled, open-label studies in weight lifters, have not found significant changes in left ventricular mass or function with androgen use [84]. The long term effects of androgen abuse on the risk of prostate and cardiovascular disease are unknown.

The anecdotal reports of "roid rage" among androgen users have received much attention in lay press. However, in placebo-controlled trials, testosterone administration has not been associated with a statistically significant increase in anger scores or measures of aggressive behaviors [63, 85_90]. It is possible that the self-reporting questionnaires lacked the sensitivity to detect small but significant changes in aggression. In controlled trials, a small number of subjects have demonstrated marked increases in aggression measures with the use of supraphysiologic doses of testosterone, while a majority of participants show little or no change, leading to speculation that high doses of androgens might provoke rage reactions in a subset of individuals with pre-existing psychopathology. Kouri et al. [88] reported that administration of supraphysiologic doses (600 mg weekly) of testosterone enanthate to healthy, young men was associated with a significant increase in aggressive responses to provocation than placebo administration. Testosterone doses that approximated the replacement doses or were slightly above the replacement dose did not produce significant changes in aggressive response in this experimental setting [88].

A wide range of psychiatric side effects, including increased aggression and hostility, and mood disturbances (e.g. depression, hypomania, and psychosis) have been reported among androgen users [91]. Dependence and withdrawal effects (such as depression) occur in a small number of steroid users. Dissatisfaction with the body and low self-esteem is common among androgen users and may predispose these individuals to the abuse of muscle building drugs [91]. Both increased and decreased sexual desire and function have been reported [61].

Breast tenderness and breast enlargement ("bitch tits" in street parlance) are frequently associated with the use of aromatizable androgens. It is not uncommon for athletes to use an aromatase inhibitor or an estrogen antagonist in combination with androgens to prevent breast enlargement.

The long-term suppression of the hypothalamic-pituitary-testicular axis with its attendant risk of dependence and continued use of androgens is a serious complication of androgen use that has not been widely appreciated. Androgen administration suppresses endogenous testosterone and sperm production by suppressing the hypothalamic-pituitary-testicular axis [92, 93]. Men using androgens may experience subfertility or infertility [94]. The recovery of the hypothalamic-pituitary axis after discontinuation of the exogenous androgen, may take weeks to months, depending on the dose and duration of prior androgen use [95_98]. During the period immediately after discontinuation of androgen use when circulating testosterone levels are low, the users experience symptoms of androgen deficiency, including loss of sexual desire and function, lack of energy, depressed mood, and hot flushes. Some patients may find these withdrawal symptoms difficult to tolerate and may revert back to using androgens, thus perpetuating the vicious cycle of abuse, withdrawal symptoms, and dependence [96_98]. Others may resort to off-label use of aromatase inhibitors or hCG obtained illicitly based on the presumption that these agents accelerate the recovery of the hypothalamic-pituitary-testicular axis, although there is no evidence to support this premise and it is possible that the use of hCG may delay the ultimate recovery of the hypothalamic-pituitary-gonadal axis.

Self administration of intramuscular injections increases the risk of infection, muscle abscess, and even sepsis [20]. Transmission of HIV infection has been reported among anabolic steroid users presumably because of needle sharing or the use of improperly sterilized needles and syringes.

Excessive muscle hypertrophy without commensurate adaptations in the associated tendons and connective tissues may predispose athletes using androgens to the risk of tendon injury and rupture and unusual stress on joints [99].

A vast majority of androgen users also abuse additional drugs [19]. Some of these additional drugs of abuse, such as cocaine, amphetamine, and ephedra may be associated with potentially serious complications.

6 Detection of illicit androgen use

Thirty four laboratories around the world have been accredited by the International Olympic Committee to perform doping tests. Traditional radioimmunoassay techniques were used initially to detect androgens in the urine specimens. However, since 1981, the accredited laboratories have used either gas chromatography-mass spectrometry (GC-MS) or in some instances liquid chromatography mass spectrometry (LC-MS) to detect androgen or their metabolites that show poor gas chromatographic properties or are temperature labile [100]. Also, during the past ten years, the introduction of the high resolution mass spectrometry (HRMS) and tandem mass spectrometry (MS/MS) has further improved the sensitivity of androgen steroid detection techniques. Derivatization of samples is often used to improve the sensitivity of the gas chromatography [101]. Thus, silylation reaction converts the polar groups such as hydroxyl and keto groups to less polar trimethylsilyl ethers and improves the signal to noise ratio [101].

For detection of testosterone abuse, the analysis of testosterone to epitestosterone ratio in conjunction with isotope ratio combustion mass spectrometry is used [102_109]. Urinary testosterone to epitestosterone ratio typically is less than 6 and is constant in any individual. There are genetic differences in testosterone to epitestosterone ratio. Administration of exogenous testosterone increases the urinary excretion of testosterone glucoronide and increases the testosterone to epitestosterone ratio. Testosterone to epitestosterone ratio greater than 4 is viewed suspiciously. Ratios greater than 4 need evaluation of previous urine samples or additional urine samples obtained after a time interval. If the high ratio is due to genetic variation, then all samples obtained from the subject would show the high ratio. A high testosterone to epitestosterone ratio that is higher than that observed in previous samples is viewed as a positive test.

If the results of the testosterone to epitestosterone ratio test are abnormal and suggest exogenous testosterone use, then additional confirmation by using gas chromatography combustion isotope ratio mass spectrometry is required [101, 104]. This method is based on the measurement of 13C/12C isotope ratio in testosterone. In nature, 1.1% of carbon exists as 13C. Synthetic androgens are synthesized from plant sterols diosgenin and stigmasterol that have less 13C than their endogenous homologs. Therefore, synthetic testosterone, in a manner similar to other synthetic organic compounds, has lower 13C to 12C ratio than a reference gas standard. During the course of the GC combustion isotope ratio mass spectrometry, the steroids are separated by gas chromatography and oxidized to carbon dioxide in a combustion chamber. The ratio of 13CO2 (m/e 45) and 12CO2 (m/e 44) is monitored in an isotope ratio mass spectrometer, and the δ value is calculated (δ value refers to the decrease in 13C relative to the reference gas with a standardized 13C to 12C ratio) [110]. A negative δ value along with a high testosterone to epitestosterone ratio suggests exogenous testosterone administration.

The procedures for the collection and transportation of samples for doping tests follow strict rules that have been established by the individual sports organizations [101]. Typically, each urine sample, collected under direct visual oversight of an accredited supervisor, is divided in to two parts (A and B samples) and transported to the testing laboratory using strict "chain of custody" procedures. If A sample is deemed positive, then B sample is analyzed in the presence of the athlete or an authorized representative of the athlete. If B sample is also positive, then doping with an androgen is confirmed, and the sports organization can impose punitive sanctions [101].

Some controversy has erupted recently over the large number of positive tests for nandrolone. Small quantities of nandrolone, 17beta-hydroxy-19-nor-4-androsten-3-one, and its metabolite 19-norandrosterone, are excreted in the urine naturally in men. The International Olympic Committee has established a threshold level of 2 ng/mL for 19-norandrosterone. Levels higher than this threshold have been reported in some individuals eating a high meat diet in conjunction with intense resistance exercise [111] and in individuals ingesting dietary supplements such as delta4-androstenedione [112].

7 The abuse of androgen precursors and designer androgens

7.1 δ-4-androstenedione

δ-4-Androstenedione is a precursor of testosterone that is converted by the enzyme 17beta hydroxy-steroid dehydrogenase to testosterone. Androstenedione witnessed a brief period of rapid growth in sales following Mark McGuire's admission of its use during an extraordinary season replete with 68 home runs. Under the Dietary Supplement Health and Education Act passed by the US Congress, for many years, androstenedione was sold over the counter as a dietary supplement [113_114]. Unlike other androgens, whose sales were regulated within the dictates of Anabolic Steroid Control Act, androstenedione's sales had not been subject to regulatory oversight of Food and Drug Administration and Drug Enforcement Agency. However, the US Congress recently added androstenedione to the list of banned anabolic steroids and it is no longer sold over the counter.

Administration of 100 mg androstenedione orally daily is associated with little or no change in circulating testosterone concentrations, while administration of 300-mg dose produces only modest increments in testosterone area-under-the-curve. However, Jasuja et al. [115] demonstrated that 500-mg androstenedione administered thrice daily for 12-weeks to hypogonadal men increased serum testosterone and free testosterone concentrations into the eugonadal range, and increased fat-free mass and muscle strength. Similarly, in women, administration of 100-mg androstenedione significantly increased serum testosterone concentrations above the physiologic range for women [116]. In female hyenas and several other mammalian species, circulating concentrations of androstenedione are higher than those in male members of these species and are associated with virilization of external genitalia and increased aggression [117]. Jasuja et al. [115] demonstrated that androstenedione binds androgen receptor albeit with a substantially lower binding affinity than testosterone, and that it promotes myogenic differentiation in a mesenchymal, multipotent cell line. Thus, androstenedione meets all the criteria for an anabolic steroid: it has structural resemblance to testosterone, it binds androgen receptor, and it promotes myogenic differentiation in vitro and when administered in sufficiently high doses, it increases muscle mass [115]. Based on these data, the US Congress recently classified androstenedione as an anabolic steroid and banned its over the counter sales.

Androstenedione administration produces substantial increments in serum estradiol and estrone concentrations [116, 118_121]. Most of the orally administered androstenedione is inactivated during its presystemic metabolism as indicated by a marked increase in its urinary metabolites, including testosterone glucuronide with only a small increase in serum testosterone [122].

The over the counter preparations of androstenedione have not been subject to the rigorous quality control required of the FDA-approved pharmaceuticals [123, 124]. Substantial variability has been observed in androstenedione content of different preparations and among different batches from the same manufacturer [112, 125]. Some batches of over the counter androstenedione have been found to contain one or more banned androgens such as nandrolone; thus, ingestion of androstenedione may result in the doping tests becoming positive [112].

7.2 Potential adverse effects of androstenedione

The long-term side effects of androstenedione use are unknown. Short term administration of androstenedione is associated with a significant increase in estradiol levels. The long-term consequences of the marked increase in estrogen levels in men taking androstenedione are unknown. In men, the increases in serum estrogen concentrations may potentially affect semen quality, increase inflammatory markers, cause gynecomastia, and induce epigenetic and cytogenetic effects on sperm.

The supplementation of androstenedione decreases HDL levels and increases low-density lipoprotein (LDL)/HDL ratio. Other adverse effects of androstenedione stem from the potential increase in testosterone levels. These may include adverse effects on plasma lipids, erythrocytosis, acne, sleep apnea, and increased risk of detecting prostate events.

Given the lack of efficacy data and total absence of long term safety data, the use of androstenedione is not clinically recommended for any indication, including the treatment of androgen deficiency in men or women.

7.3 Dehydroepiandrosterone (DHEA)

DHEA is a weak androgen by itself, but it is converted in peripheral tissues to testosterone and estradiol. In addition to being a weak androgen and an androgen precursor, DHEA has been shown to function as a neurosteroid [126].

DHEA binds androgen receptor with a binding affinity that is substantially lower than that of dihydro-testosterone (DHT). A separate G-protein coupled membrane receptor for DHEA has been proposed [127]; however, the existence of such a DHEA-specific membrane receptor has not been confirmed. DHEA also has been shown to modulate the activities of N-methyl-D-aspartate (NMDA) and γ-amino-butyric acid (GABA) receptors [128].

The literature on DHEA is difficult to interpret. DHEA studies in rodents have limited applicability to humans, because rodents have very little endogenous circulating DHEA. Many DHEA studies reporting beneficial neurotropic and anti-cancer effects, and immune enhancement were conducted in rodents.

The human trials of DHEA have been characterized by heterogeneity of doses, formulations, and study populations. DHEA studies have been conducted in patients with adrenal insufficiency [129_133], older men and women [134_139], peri- and post-menopausal women [140, 141], and in patients with autoimmune disease [142_144]. These trials used doses as high as 1500 mg daily and as low as 25 mg daily. Most human trials used 50 mg DHEA daily for three to six months, included small samples, and were of relatively short durations.

A Cochrane review of DHEA trials concluded that there was insufficient evidence of beneficial effect of DHEA on cognition in older men and women [138, 139]. One randomized trial has reported greater improvements in bone mineral density in older men and women receiving 50 mg DHEA daily than with placebo [145].

DHEA trials in women with adrenal insufficiency have yielded inconsistent results. Arlt et al. [129] used a double-blind, placebo-controlled, crossover study design in women with primary or secondary adrenal insufficiency who received either placebo or 50 mg DHEA daily for 16 weeks each. DHEA administration was associated with improvements in scores for depression and anxiety, sexual function, and circulating osteocalcin levels, but no significant changes in body composition [122]. Other trials of DHEA supplementation in women with adrenal insufficiency failed to confirm the beneficial effects of DHEA on mood, well being or sexual function that were observed in the Arlt study [130_132]. DHEA has not been shown to consistently improve body composition, physical function, or insulin sensitivity. The effects of DHEA administration on cardiovascular event rates or cancer incidence rates are unknown.

In a placebo-controlled trial that used pharmacological doses of DHEA (200 mg daily), modest improvements in lupus outcomes and a greater reduction in disease flares and disease activity were reported in patients receiving DHEA than in those receiving placebo [142_144]. The effects of DHEA on bone mineral density in patients with SLE have been inconsistent.

Thus, the efficacy of DHEA has not been demonstrated in any disease state and DHEA use cannot be recommended for any clinical indication at present.

7.4 Other androgen precursors and designer steroids

Precursors of testosterone (4-androstenediol and 5-androstenediol in addition to 4-androstenedione and DHEA discussed above), dihydrotestosterone (5-alpha-androstane-3beta-17 beta-diol, 5-alpha-androstane-3 alpha, 17 beta diol, 5-alpha-androstane-3, 17 dione, 5-alpha-androst-1-ene-3, 17 dione, 17 beta-hydroxy-5-alpha-androst-1-en-3-one, 5-alpha-androst, 1-ene, 17 beta-diol) or nortestosterone (4-norandrostenedione, 4-norandrostenediol, and 5-norandrostenediol) [101] that are weakly androgenic by themselves, but that are converted in the body to potent androgens, have become available on the internet. Even a precursor (androsta-1,4-diene-3, 17-dione) of boldenone (17-beta-hydrox-yandrosta-1, 4-dien-3-one) has been introduced [101].

The androgens abused by athletes had been synthesized initially for medicinal or veterinary indications. However, recent years have witnessed the appearance of designer steroids, such as tetrahydrogestrinone (THG) [146, 147] and madol [148] that were developed solely for abuse [149]. The detection of these novel androgens has proven challenging to the testing laboratories because detection methods have not been standardized for these new designer androgens. These designer compounds have not undergone any formal toxicological or safety testing in animals or humans; consequently, their growing use by athletes poses significant health concerns. The government agencies have found themselves stymied in their efforts to regulate this underground marketplace of designer steroids because there are no published data with the use of these novel designer steroids, and generating new data of their androgenic and anabolic efficacy that would withstand scientific and legal scrutiny is a time consuming and laborious task.

8 Conclusion

The abuse of androgens by athletes and recreational body builders is wide spread and worldwide. Androgens increase skeletal muscle mass through their effects on mesenchymal stem cell differentiation through an androgen receptor-mediated mechanism. In spite of significant improvement in detection methods, the problem of doping in sports is unlikely to disappear anytime soon because of societal values and economic incentives that emphasize winning at all costs and because of the lack of will on the part of governments throughout the world to enforce stricter screening and penalties.

References

1 Kahn A. Regaining lost youth: the controversial and colorful beginnings of hormone replacement therapy in aging. J Gerontol A Biol Sci Med Sci 2005; 60: 142_7.

2 Freeman ER, Bloom DA, McGuire EJ. A brief history of testosterone. J Urol 2001; 165: 371_3.

3 Yesalis CE, Bahrke MS. Anabolic-androgenic steroids. Current issues. Sports Med 1995; 19: 326_40.

4 Brown-Sequard CE. The effects produced in man by subcutaneous injections of a liquid obtained from testicles of animals. Lancet 1889; 2: 105_7.

5 Boje O. Doping. Bulletin of Health Organization of the League of Nations. 1939; 8: 439_69.

6 Wade N. Anabolic steroids: doctors denounce then but athletes aren't listening. Science 1972; 176: 1399_403.

7 Bahrke MS, Yesalis CE. Abuse of anabolic androgenic steroids and related substances in sport and exercise. Curr Opin Pharmacol 2004; 4: 614_20.

8 Yesalis CE 3rd, Bahrke MS, Kopstein AN, Baruskiewicz CK. Incidence onabolic steroid use: a discussion of methodological issues. In: Yesalis CE 3rd, editor. Anabolic Steroids in Sports and Exercise. 2nd edn. Champaign: Human Kinetics; 2000, p73_115.

9 Yesalis CE, Kennedy NJ, Kopstein AN, Bahrke MS. Anabolic-androgenic steroid use in the United States. JAMA 1993; 270: 1217_21.

10 Bahrke MS, Yesalis CE, Kopstein AN, Stephens JA. Risk factors associated with anabolic-androgenic steroid use among adolescents. Sports Med 2000; 29: 397_405.

11 Yesalis CE, Barsukiewicz CK, Kopstein AN, Bahrke MS. Trends in anabolic-androgenic steroid use among adolescents. Arch Pediatr Adolesc Med 1997; 151: 1197_206.

12 Buckley WE, Yesalis CE 3rd, Friedl KE, Anderson WA, Streit AL, Wright JE. Estimated prevalence of anabolic steroid use among male high school seniors. JAMA 1988; 260: 3441_5.

13 Irving LM, Wall M, Neumark-Sztainer D, Story M. Steroid use among adolescents: findings from project EAT. J Adolescent Health 2002; 30: 243_52.

14 Melia P, Pipe A, Greenberg L. The use of anabolic-androgenic steroids by Canadian students. Clin J Sport Med 1996; 6: 9_14.

15 Handelsman DJ, Gupta L. Prevalence and risk factors for anabolic-androgenic steroid abuse in Australian high school students. Int J Androl 1997; 20: 159_64.

16 Franke WW, Berendonk B. Hormonal doping and androgenization of athletes: a secret program of the German Democratic Republic government. Clin Chem 1997; 43: 1262_79.

17 McCabe SE, Brower KJ, West BT, Nelson TF, Wechsler H. Trends in non-medical use of anabolic steroids by U.S. college students: results from four national surveys. Drug Alcohol Depend 2007; 90: 243_51.

18 Mornitoring the Future. http://www.monitoringthefuture.org

19 Evans NA. Gym and tonic: a profile of 100 male steroid users. Br J Sports Med 1997; 31: 54_8.

20 Evans NA. Local complications of self administered anabolic steroid injections. Br J Sports Med 1997; 31: 349_50.

21 Pope HG Jr., Katz DL. Psychiatric and medical effects of anabolic-androgenic steroid use. A controlled study of 160 athletes. Arch Gen Psychiatry 1994; 51: 375_82.

22 Bhasin S, Storer TW, Berman N, Callegari C, Clevenger B, Phillips J, et al. The effects of supraphysiologic doses of testosterone on muscle size and strength in normal men. N Engl J Med 1996; 335: 1_7.

23 Bhasin S, Woodhouse L, Casaburi R, Singh AB, Bhasin D, Berman N, et al. Testosterone dose-response relationships in healthy young men. Am J Physiol Endocrinol Metab 2001; 281: E1172_81.

24 Storer TW, Magliano L, Woodhouse L, Lee ML, Dzekov C, Dzekov J, et al. Testosterone dose-dependently increases maximal voluntary strength and leg power, but does not affect fatigability or specific tension. J Clin Endocrinol Metab 2003; 88: 1478_85.

25 Bhasin S, Calof OM, Storer TW, Lee ML, Mazer NA, Jasuja R, et al. Drug insight: testosterone and selective androgen receptor modulators as anabolic therapies for chronic illness and aging.Nat Clin Pract Endocrinol Metab 2006; 2: 146_59.

26 Bhasin S, Cunningham GR, Hayes FJ, Matsumoto AM, Snyder PJ, Swerdloff RS, et al. Testosterone therapy in adult men with androgen deficiency syndromes: an endocrine society clinical practice guideline. J Clin Endocrinol Metab 2006; 91: 1995_2010.

27 Wilson JD. Androgen abuse by athletes. Endocr Rev 1988; 9: 181_99.

28 Bhasin S, Woodhouse L, Storer TW. Proof of the effect of testosterone on skeletal muscle. J Endocrinol 2001; 170: 27_38.

29 Bhasin S, Woodhouse L, Casaburi R, Singh AB, Mac RP, Lee M, et al. Older men are as responsive as young men to the anabolic effects of graded doses of testosterone on the skeletal muscle. J Clin Endocrinol Metab 2005; 90: 678_88.

30 Woodhouse LJ, Reisz-Porszasz S, Javanbakht M, Storer TW, Lee M, Zerounian H, et al. Development of models to predict anabolic response to testosterone administration in healthy young men. Am J Physiol Endocrinol Metab 2003; 284: E1009_17.

31 Bhasin S, Storer TW, Berman N, Yarasheski KE, Clevenger B, Phillips J, et al. Testosterone replacement increases fat-free mass and muscle size in hypogonadal men. J Clin Endocrinol Metab 1997; 82: 407_13.

32 Brodsky IG, Balagopal P, Nair KS. Effects of testosterone replacement on muscle mass and muscle protein synthesis in hypogonadal men—a clinical research center study. J Clin Endocrinol Metab 1996; 81: 3469_75.

33 Snyder PJ, Peachey H, Berlin JA, Hannoush P, Haddad G, Dlewati A, et al. Effects of testosterone replacement in hypogonadal men. J Clin Endocrinol Metab 2000; 85: 2670_7.

34 Wang C, Swedloff RS, Iranmanesh A, Dobs A, Snyder PJ, Cunningham G, et al. Transdermal testosterone gel improves sexual function, mood, muscle strength, and body composition parameters in hypogonadal men. Testosterone Gel Study Group. J Clin Endocrinol Metab 2000; 85: 2839_53.

35 Katznelson L, Finkelstein JS, Schoenfeld DA, Rosenthal DI, Anderson EJ, Klibanski A. Increase in bone density and lean body mass during testosterone administration in men with acquired hypogonadism. J Clin Endocrinol Metab 1996; 81: 4358_65.

36 Baume N, Schumacher YO, Sottas PE, Bagutti C, Cauderay M, Mangin P, et al. Effect of multiple oral doses of androgenic anabolic steroids on endurance performance and serum indices of physical stress in healthy male subjects. Eur J Appl Physiol 2006; 98: 329_40.

37 Georgieva KN, Boyadjiev NP. Effects of nandrolone decanoate on VO2max, running economy, and endurance in rats. Med Sci Sports Exerc 2004; 36: 1336_41.

38 Hendler ED, Solomon LR. Prospective controlled study of androgen effects on red cell oxygen transport and work capacity in chronic hemodialysis patients. Acta Haematol 1990; 83: 1_8.

39 Blanco CE, Popper P, Micevych P. Anabolic-androgenic steroid induced alterations in choline acetyltransferase messenger RNA levels of spinal cord motoneurons in the male rat. Neuroscience 1997; 78: 873_82.

40 Blanco CE, Zhan WZ, Fang YH, Sieck GC. Exogenous testosterone treatment decreases diaphragm neuromuscular transmission failure in male rats. J Appl Physiol 2001; 90: 850_6.

41 Sinha-Hikim I, Artaza J, Woodhouse L, Gonzalez-Cadavid N, Singh AB, Lee MI, et al. Testosterone-induced increase in muscle size in healthy young men is associated with muscle fiber hypertrophy. Am J Physiol Endocrinol Metab 2002; 283: E154_64.

42 Sinha-Hikim I, Roth SM, Lee MI, Bhasin S. Testosterone-induced muscle hypertrophy is associated with an increase in satellite cell number in healthy, young men. Am J Physiol Endocrinol Metab 2003; 285: E197_205.

43 Sinha-Hikim I, Taylor WE, Gonzalez-Cadavid NF, Zheng W, Bhasin S. Androgen receptor in human skeletal muscle and cultured muscle satellite cells: up-regulation by androgen treatment. J Clin Endocrinol Metab 2004; 89: 5245_55.

44 Bhasin S, Taylor WE, Singh R, Artaza J, Sinha-Hikim I, Jasuja R, et al. The mechanisms of androgen effects on body composition: mesenchymal pluripotent cell as the target of androgen action. J Gerontol A Biol Sci Med Sci 2003; 58: M1103_10.

45 Singh R, Artaza JN, Taylor WE, Braga M, Yuan X, Gonzalez-Cadavid NF, et al. Testosterone inhibits adipogenic differentiation in 3T3-L1 cells: nuclear translocation of androgen receptor complex with beta-catenin and T-cell factor 4 may bypass canonical Wnt signaling to down-regulate adipogenic transcription factors. Endocrinology 2006; 147: 141_54.

46 Singh R, Artaza JN, Taylor WE, Gonzalez-Cadavid NF, Bhasin S. Androgens stimulate myogenic differentiation and inhibit adipogenesis in C3H 10T1/2 pluripotent cells through an androgen receptor-mediated pathway. Endocrinology 2003; 144: 5081_8.

47 Doumit ME, Cook DR, Merkel RA. Testosterone up-regulates androgen receptors and decreases differentiation of porcine myogenic satellite cells in vitro. Endocrinology 1996; 137: 1385_94.

48 Joubert Y, Tobin C. Satellite cell proliferation and increase in the number of myonuclei induced by testosterone in the levator ani muscle of the adult female rat. Dev Biol 1989; 131: 550_7.

49 Joubert Y, Tobin C. Testosterone treatment results in quiescent satellite cells being activated and recruited into cell cycle in rat levator ani muscle. Dev Biol 1995; 169: 286_94.

50 Mulvaney DR, Marple DN, Merkel RA. Proliferation of skeletal muscle satellite cells after castration and administration of testosterone propionate. Proc Soc Exp Biol Med 1988; 188: 40_5.

51 Nnodim JO. Testosterone mediates satellite cell activation in denervated rat levator ani muscle. Anat Rec 2001; 263: 19_24.

52 Ferrando AA, Sheffield-Moore M, Paddon-Jones D, Wolfe RR, Urban RJ. Differential anabolic effects of testosterone and amino acid feeding in older men. J Clin Endocrinol Metab 2003; 88: 358_62.

53 Ferrando AA, Sheffield-Moore M, Wolf SE, Herndon DN, Wolfe RR. Testosterone administration in severe burns ameliorates muscle catabolism. Crit Care Med 2001; 29: 1936_42.

54 Ferrando AA, Sheffield-Moore M, Yeckel CW, Gilkison C, Jiang J, Achacosa A, et al. Testosterone administration to older men improves muscle function: molecular and physiological mechanisms. Am J Physiol Endocrinol Metab 2002; 282: E601_7.

55 Glazer G. Atherogenic effects of anabolic steroids on serum lipid levels. A literature review. Arch Intern Med 1991; 151: 1925_33.

56 Ansell JE, Tiarks C, Fairchild VK. Coagulation abnormalities associated with the use of anabolic steroids. Am Heart J 1993; 125: 367_71.

57 Soe KL, Soe M, Gluud C. Liver pathology associated with the use of anabolic-androgenic steroids. Liver 1992; 12: 73_9.

58 Dickerman RD, Pertusi RM, Zachariah NY, Dufour DR, McConathy WJ. Anabolic steroid-induced hepatotoxicity: is it overstated? Clin J Sport Med 1999; 9: 34_9.

59 Pertusi R, Dickerman RD, McConathy WJ. Evaluation of aminotransferase elevations in a bodybuilder using anabolic steroids: hepatitis or rhabdomyolysis? J Am Osteopath Assoc 2001; 101: 391_4.

60 Socas L, Zumbado M, Perez-Luzardo O, Ramos A, Perez C, Hernandez JR, et al. Hepatocellular adenomas associated with anabolic androgenic steroid abuse in bodybuilders: a report of two cases and a review of the literature. Br J Sports Med 2005; 39: e27.

61 Bonetti A, Tirelli F, Catapano A, Dazzi D, Dei Cas A, Solito F, et al. Side effects of anabolic androgenic steroids abuse. Int J Sports Med 2007; Nov 14 [Epub ahead of print].

62 Bahrke MS, Yesalis CE 3rd, Wright JE. Psychological and behavioural effects of endogenous testosterone and anabolic-androgenic steroids. An update. Sports Med 1996; 22: 367_90.

63 Su TP, Pagliaro M, Schmidt PJ, Pickar D, Wolkowitz O, Rubinow DR. Neuropsychiatric effects of anabolic steroids in male normal volunteers. JAMA 1993; 269: 2760_4.

64 Patil JJ, O'Donohoe B, Loyden CF, Shanahan D. Near-fatal spontaneous hepatic rupture associated with anabolic androgenic steroid use: a case report. Br J Sports Med 2007; 41: 462_3.

65 Calof O, Singh AB, Lee ML, Urban RJ, Kenny AM, Tenover JL, et al. Adverse events associated with testosterone supplementation of older men. J Greontol Med Sci 2006; 2: 146_59.

66 Wight JN Jr, Salem D. Sudden cardiac death and the "athlete's heart". Arch Intern Med 1995; 155: 1473_80.

67 Melchert RB, Welder AA. Cardiovascular effects of androgenic-anabolic steroids. Med Sci Sports Exerc 1995; 27: 1252_62.

68 Karila TA, Karjalainen JE, Mantysaari MJ, Viitasalo MT, Seppala TA. Anabolic androgenic steroids produce dose-dependant increase in left ventricular mass in power atheletes, and this effect is potentiated by concomitant use of growth hormone. Int J Sports Med 2003; 24: 337_43.

69 Parssinen M, Kujala U, Vartiainen E, Sarna S, Seppala T. Increased premature mortality of competitive powerlifters suspected to have used anabolic agents. Int J Sports Med 2000; 21: 225_7.

70 Cohen JC, Hickman R. Insulin resistance and diminished glucose tolerance in powerlifters ingesting anabolic steroids. J Clin Endocrinol Metab 1987; 64: 960_3.

71 Sullivan ML, Martinez CM, Gennis P, Gallagher EJ. The cardiac toxicity of anabolic steroids. Prog Cardiovasc Dis 1998; 41: 1_15.

72 Lenders JW, Demacker PN, Vos JA, Jansen PL, Hoitsma AJ, van't Laar A, et al. Deleterious effects of anabolic steroids on serum lipoproteins, blood pressure, and liver function in amateur body builders. Int J Sports Med 1988; 9: 19_23.

73 De Piccoli B, Giada F, Benettin A, Sartori F, Piccolo E. Anabolic steroid use in body builders: an echocardiographic study of left ventricle morphology and function. Int J Sports Med 1991; 12: 408_12.

74 Dickerman RD, Schaller F, Zachariah NY, McConathy WJ. Left ventricular size and function in elite bodybuilders using anabolic steroids. Clin J Sport Med 1997; 7: 90_3.

75 Salke RC, Rowland TW, Burke EJ. Left ventricular size and function in body builders using anabolic steroids. Med Sci Sports Exerc 1985;17: 701_4.

76 Zuliani U, Bernardini B, Catapano A, Campana M, Cerioli G, Spattini M. Effects of anabolic steroids, testosterone, and HGH on blood lipids and echocardiographic parameters in body builders. Int J Sports Med 1989; 10: 62_6.

77 Pearson AC, Schiff M, Mrosek D, Labovitz AJ, Williams GA. Left ventricular diastolic function in weight lifters. Am J Cardiol 1986; 58: 1254_9.

78 Urhausen A, Albers T, Kindermann W. Are the cardiac effects of anabolic steroid abuse in strength athletes reversible? Heart 2004; 90: 496_501.

79 Graham MR, Grace FM, Boobier W, Hullin D, Kicman A, Cowan D, et al. Homocysteine induced cardiovascular events: a consequence of long term anabolic-androgenic steroid (AAS) abuse. Br J Sports Med 2006; 40: 644_8.

80 Nieminen MS, Ramo MP, Viitasalo M, Heikkila P, Karjalainen J, Mantysaari M, et al. Serious cardiovascular side effects of large doses of anabolic steroids in weight lifters. Eur Heart J 1996; 17: 1576_83.

81 Payne JR, Kotwinski PJ, Montgomery HE. Cardiac effects of anabolic steroids. Heart 2004; 90: 473_5.

82 D'Andrea A, Caso P, Salerno G, Scarafile R, De Corato G, Mita C, et al. Left ventricular early myocardial dysfunction after chronic misuse of anabolic androgenic steroids: a Doppler myocardial and strain imaging analysis. Br J Sports Med 2007; 41: 149_55.

83 Chung T, Kelleher S, Liu PY, Conway AJ, Kritharides L, Handelsman DJ. Effects of testosterone and nandrolone on cardiac function: a randomized, placebo-controlled study. Clin Endocrinol (Oxf) 2007; 66: 235_45.

84 Hartgens F, Cheriex EC, Kuipers H. Prospective echocardio-graphic assessment of androgenic-anabolic steroids effects on cardiac structure and function in strength athletes. Int J Sports Med 2003; 24: 344_51.

85 Tricker R, Casaburi R, Storer TW, Clevenger B, Berman N, Shirazi A, et al. The effects of supraphysiological doses of testosterone on angry behavior in healthy eugonadal men—a clinical research center study. J Clin Endocrinol Metab 1996; 81: 3754_8.

86 Daly RC, Su TP, Schmidt PJ, Pagliaro M, Pickar D, Rubinow DR. Neuroendocrine and behavioral effects of high-dose anabolic steroid administration in male normal volunteers. Psychoneuroendo-crinology 2003; 28: 317_31.

87 Yates WR, Perry PJ, MacIndoe J, Holman T, Ellingrod V. Psychosexual effects of three doses of testosterone cycling in normal men. Biol Psychiatry 1999; 45: 254_60.

88 Kouri EM, Lukas SE, Pope HG Jr, Oliva PS. Increased aggressive responding in male volunteers following the administration of gradually increasing doses of testosterone cypionate. Drug Alcohol Depend 1995; 40: 73_9.

89 Pope HG Jr, Kouri EM, Hudson JI. Effects of supraphysiologic doses of testosterone on mood and aggression in normal men: a randomized controlled trial. Arch Gen Psychiatry 2000; 57: 133_40.

90 Anderson RA, Bancroft J, Wu FC. The effects of exogenous testosterone on sexuality and mood of normal men. J Clin Endocrinol Metab 1992; 75: 1503_7.

91 Pagonis TA, Angelopoulos NV, Koukoulis GN, Hadjichristodoulou CS. Psychiatric side effects induced by supraphysiological doses of combinations of anabolic steroids correlate to the severity of abuse. Eur Psychiatry 2006; 21: 551_62.

92 Gill GV. Anabolic steroid induced hypogonadism treated with human chorionic gonadotropin. Postgrad Med J 1998; 74: 45_6.

93 MacIndoe JH, Perry PJ, Yates WR, Holman TL, Ellingrod VL, Scott SD. Testosterone suppression of the HPT axis. J Investig Med 1997; 45: 441_7.

94 Lloyd FH, Powell P, Murdoch AP. Anabolic steroid abuse by body builders and male subfertility. BMJ 996; 313: 100_1.

95 Jarow JP, Lipshultz LI. Anabolic steroid-induced hypogonadotropic hypogonadism. Am J Sports Med 1990; 18: 429_31.

96 Brower KJ. Anabolic steroid abuse and dependence. Curr Psychiatry Rep 2002; 4: 377_87.

97 Brower KJ, Blow FC, Young JP, Hill EM. Symptoms and correlates of anabolic-androgenic steroid dependence. Br J Addict 1991; 86: 759_68.

98 Brower KJ, Eliopulos GA, Blow FC, Catlin DH, Beresford TP. Evidence for physical and psychological dependence on anabolic androgenic steroids in eight weight lifters. Am J Psychiatry 1990; 147: 510_2.

99 Evans NA, Bowrey DJ, Newman GR. Ultrastructural analysis of ruptured tendon from anabolic steroid users. Injury 1998; 29: 769_73.

100 Schanzer W. Metabolism of anabolic androgenic steroids. Clin Chem 1996; 42: 1001_20.

101 Schanzer W. Abuse of androgens and detection of illegal use. In: Nieschlag E, Behre HM, editors. Testosterone: Action, Deficiency, Substitution. 3rd edn. Cambridge: Cambridge University Press; 2004. p715_36.

102 Aguilera R, Becchi M, Grenot C, Casabianca H, Hatton CK. Detection of testosterone misuse: comparison of two chromatographic sample preparation methods for gas chromatographic-combustion/isotope ratio mass spectrometric analysis. J Chromatogr B Biomed Appl 1996; 687: 43_53.

103 Aguilera R, Chapman TE, Starcevic B, Hatton CK, Catlin DH. Performance characteristics of a carbon isotope ratio method for detecting doping with testosterone based on urine diols: controls and athletes with elevated testosterone/epitestosterone ratios. Clin Chem 2001; 47: 292_300.

104 Catlin DH, Hatton CK, Starcevic SH. ssues in detecting abuse of xenobiotic anabolic steroids and testosterone by analysis of athletes' urine. Clin Chem 1997; I 43: 1280_8.

105 Garle M, Ocka R, Palonek E, Bjorkhem I. Increased urinary testosterone/epitestosterone ratios found in Swedish athletes in connection with a national control program. Evaluation of 28 cases. J Chromatogr B Biomed Appl 1996; 687: 55_9.

106 Gonzalo-Lumbreras R, Pimentel-Trapero D, Izquierdo-Hornillos R. Development and method validation for testosterone and epitestosterone in human urine samples by liquid chromatography applications. J Chromatogr Sci 2003; 41: 261_5.

107 Hebestreit M, Flenker U, Buisson C, Andre F, Le Bizec B, Fry H, et al. Application of stable carbon isotope analysis to the detection of testosterone administration to cattle. J Agric Food Chem 2006; 54: 2850_8.

108 Saudan C, Baume N, Robinson N, Avois L, Mangin P, Saugy M. Testosterone and doping control. Br J Sports Med 2006; 40 (Suppl 1): i21_4.

109 Sottas PE, Baume N, Saudan C, Schweizer C, Kamber M, Saugy M. Bayesian detection of abnormal values in longitudinal biomarkers with an application to T/E ratio. Biostatistics 2007; 8: 285_96.

110 Shackleton CH, Phillips A, Chang T, Li Y. Confirming testosterone administration by isotope ratio mass spectrometric analysis of urinary androstanediols. Steroids 1997; 62: 379_87.

111 Le Bizec B, Gaudin I, Monteau F, Andre F, Impens S, De Wasch K, et al. Consequence of boar edible tissue consumption on urinary profiles of nandrolone metabolites. I. Mass spectrometric detection and quantification of 19-norandrosterone and 19-noretiocholanolone in human urine. Rapid Commun Mass Spectrom 2000; 14: 1058_65.

112 Catlin DH, Leder BZ, Ahrens B, Starcevic B, Hatton CK, Green GA, et al. Trace contamination of over-the-counter androstenedione and positive urine test results for a nandrolone metabolite. JAMA 2000; 284: 2618_21.

113 Kottke MK. Scientific and regulatory aspects of nutraceutical products in the United States. Drug Dev Ind Pharm 1998; 24: 1177_95.

114 Stevens K. Dietary Supplement Health and Education Act: quiet but far-reaching consequences. Altern Ther Health Med 1995; 1: 17_8.

115 Jasuja R, Ramaraj P, Mac RP, Singh AB, Storer TW, Artaza J, et al. Delta-4-androstene-3,17-dione binds androgen receptor, promotes myogenesis in vitro, and increases serum testosterone levels, fat-free mass, and muscle strength in hypogonadal men. J Clin Endocrinol Metab 2005; 90: 855_63.

116 Leder BZ, Leblanc KM, Longcope C, Lee H, Catlin DH, Finkelstein JS. Effects of oral androstenedione administration on serum testosterone and estradiol levels in postmenopausal women. J Clin Endocrinol Metab 2002; 87: 5449_54.

117 Glickman SE, Coscia EM, Frank LG, Licht P, Weldele ML, Drea CM. Androgens and masculinization of genitalia in the spotted hyaena (Crocuta crocuta). 3. Effects of juvenile gonadectomy. J Reprod Fertil 1998; 113: 129_35.

118 Leder BZ, Longcope C, Catlin DH, Ahrens B, Schoenfeld DA, Finkelstein JS. Oral androstenedione administration and serum testosterone concentrations in young men. JAMA 2000; 283: 779_82.

119 Brown GA, Vukovich MD, Martini ER, Kohut ML, Franke WD, Jackson DA, et al. Endocrine responses to chronic androstenedione intake in 30- to 56-year-old men. J Clin Endocrinol Metab 2000; 85: 4074_80.

120 Brown GA, Vukovich MD, Martini ER, Kohut ML, Franke WD, Jackson DA, et al. Effects of androstenedione-herbal supplementation on serum sex hormone concentrations in 30- to 59-year-old men. Int J Vitam Nutr Res 2001; 71: 293_301.

121 King DS, Sharp RL, Vukovich MD, Brown GA, Reifenrath TA, Uhl NL, et al. Effect of oral androstenedione on serum testosterone and adaptations to resistance training in young men: a randomized controlled trial. JAMA 1999; 281: 2020_8.

122 Leder BZ, Catlin DH, Longcope C, Ahrens B, Schoenfeld DA, Finkelstein JS. Metabolism of orally administered androstenedione in young men. J Clin Endocrinol Metab 2001; 86: 3654_8.

123 Delbeke FT, Van Eenoo P, Van Thuyne W, Desmet N. Prohor-mones and sport. J Steroid Biochem Mol Biol 2002; 83: 245_51.

124 van der Merwe PJ, Grobbelaar E. Unintentional doping through the use of contaminated nutritional supplements. S Afr Med J 2005; 95: 510_1.

125 Geyer H, Parr MK, Mareck U, Reinhart U, Schrader Y, Schanzer W. Analysis of non-hormonal nutritional supplements for anabolic-androgenic steroids - results of an international study. Int J Sports Med 2004; 25: 124_9.

126 Baulieu EE, Robel P. Dehydroepiandrosterone (DHEA) and dehydroepiandrosterone sulfate (DHEAS) as neuroactive neurosteroids. Proc Natl Acad Sci U S A 1998; 95: 4089_91.

127 Liu D, Dillon JS. Dehydroepiandrosterone activates endothelial cell nitric-oxide synthase by a specific plasma membrane receptor coupled to Galpha(i2,3). J Biol Chem 2002; 277: 21379_88.

128 Demirgoren S, Majewska MD, Spivak CE, London ED. Receptor binding and electrophysiological effects of dehydroepiandro-sterone sulfate, an antagonist of the GABAA receptor. Neuroscience 1991; 45: 127_35.

129 Arlt W, Callies F, van Vlijmen JC, Koehler I, Reincke M, Bidlingmaier M, et al. Dehydroepiandrosterone replacement in women with adrenal insufficiency. N Engl J Med 1999; 341: 1013_20.

130 Hunt PJ, Gurnell EM, Huppert FA, Richards C, Prevost AT, Wass JA, et al. Improvement in mood and fatigue after dehydro-epiandrosterone replacement in Addison's disease in a randomized, double blind trial. J Clin Endocrinol Metab 2000; 85: 4650_6.

131 Lovas K, Gebre-Medhin G, Trovik TS, Fougner KJ, Uhlving S, Nedrebo BG, et al. Replacement of dehydroepiandrosterone in adrenal failure: no benefit for subjective health status and sexuality in a 9-month, randomized, parallel group clinical trial. J Clin Endocrinol Metab 2003; 88: 1112_8.

132 Johannsson G, Burman P, Wiren L, Engstrom BE, Nilsson AG, Ottosson M, et al. Low dose dehydroepiandrosterone affects behavior in hypopituitary androgen-deficient women: a placebo-controlled trial. J Clin Endocrinol Metab 2002; 87: 2046_52.

133 Gebre-Medhin G, Husebye ES, Mallmin H, Helstrom L, Berne C, Karlsson FA, et al. Oral dehydroepiandrosterone (DHEA) replacement therapy in women with Addison's disease. Clin Endocrinol (Oxf) 2000; 52: 775_80.

134 Morales AJ, Haubrich RH, Hwang JY, Asakura H, Yen SS. The effect of six months treatment with a 100 mg daily dose of dehydroepiandrosterone (DHEA) on circulating sex steroids, body composition and muscle strength in age-advanced men and women. Clin Endocrinol (Oxf) 1998; 49: 421_32.

135 Arlt W, Callies F, Koehler I, van Vlijmen JC, Fassnacht M, Strasburger CJ, et al. Dehydroepiandrosterone supplementation in healthy men with an age-related decline of dehydroepiandrosterone secretion. J Clin Endocrinol Metab 2001; 86: 4686_92.

136 Callies F, Arlt W, Siekmann L, Hubler D, Bidlingmaier F, Allolio B. Influence of oral dehydroepiandrosterone (DHEA) on urinary steroid metabolites in males and females. Steroids 2000; 65: 98_102.

137 Wolkowitz OM, Reus VI, Keebler A, Nelson N, Friedland M, Brizendine L, et al. Double-blind treatment of major depression with dehydroepiandrosterone. Am J Psychiatry 1999; 156: 646_9.

138 Huppert FA, van Niekerk JK. Dehydroepiandrosterone (DHEA) supplementation for cognitive function. Cochrane review. In: Cochrane Library. Chichester, UK: John Wiley and Sons Ltd., 2003. CD000304.

139 Flynn MA, Weaver-Osterholtz D, Sharpe-Timms KL, Allen S, Krause G. Dehydroepiandrosterone replacement in aging humans. J Clin Endocrinol Metab 1999; 84: 1527_33.

140 Genazzani AD, Stomati M, Bernardi F, Pieri M, Rovati L, Genazzani AR. Long-term low-dose dehydroepiandrosterone oral supplementation in early and late postmenopausal women modulates endocrine parameters and synthesis of neuroactive steroids. Fertil Steril 2003; 80: 1495_501.

141 Barnhart KT, Freeman E, Grisso JA, Rader DJ, Sammel M, Kapoor S, et al. The effect of dehydroepiandrosterone supplementation to symptomatic perimenopausal women on serum endocrine profiles, lipid parameters, and health-related quality of life. J Clin Endocrinol Metab 1999; 84: 3896_902.

142 Chang DM, Lan JL, Lin HY, Luo SF. Dehydroepiandrosterone treatment of women with mild-to-moderate systemic lupus erythematosus: a multicenter randomized, double-blind, placebo-controlled trial. Arthritis Rheum 2002; 46: 2924_7.

143 Hartkamp A, Geenen R, Godaert GL, Bijl M, Bijlsma JW, Derksen RH. The effect of dehydroepiandrosterone on lumbar spine bone mineral density in patients with quiescent systemic lupus erythematosus. Arthritis Rheum 2004; 50: 3591_5.

144 van Vollenhoven RF, Park JL, Genovese MC, West JP, McGuire JL. A double-blind, placebo-controlled, clinical trial of dehydroepiandrosterone in severe systemic lupus erythematosus. Lupus 1999; 8: 181_7.

145 Jankowski CM, Gozansky WS, Schwartz RS, Dahl DJ, Kittelson JM, Scott SM, et al. Effects of dehydroepiandrosterone replacement therapy on bone mineral density in older adults: a randomized, controlled trial. J Clin Endocrinol Metab 2006; 91: 2986_93.

146 Catlin DH, Sekera MH, Ahrens BD, Starcevic B, Chang YC, Hatton CK. Tetrahydrogestrinone: discovery, synthesis, and detection in urine. Rapid Commun Mass Spectrom 2004; 18: 1245_9.

147 Jasuja R, Catlin DH, Miller A, Chang YC, Herbst KL, Starcevic B, et al. Tetrahydrogestrinone is an androgenic steroid that stimulates androgen receptor-mediated, myogenic differentiation in C3H10T1/2 multipotent mesenchymal cells and promotes muscle accretion in orchidectomized male rats. Endocrinology 2005; 146: 4472_8.

148 Sekera MH, Ahrens BD, Chang YC, Starcevic B, Georgakopoulos C, Catlin DH. Another designer steroid: discovery, synthesis, and detection of `madol' in urine. Rapid Commun Mass Spectrom 2005; 19: 781_4.

149 Handelsman DJ. Designer androgens in sport: when too much is never enough. Sci STKE 2004: pe41.

 
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