Aim: To analyze factors influencing the efficacy of hormonal suppression of spermatogenesis for male contraception.

Methods: A nested case-control study was conducted, involving 43 subjects, who did not achieve azoospermia or severe oligozoospermia when given monthly injections of 500 mg testosterone undecanoate (TU), defined as partial suppressors compared with 855 subjects who had suppressed spermatogenesis (complete suppressors). Sperm density, serum testosterone, luteinizing hormone (LH) and follicle stimulating hormone (FSH) concentrations at the baseline and the suppression phase were compared between partial and complete suppressors. Polymorphisms of androgen receptor (AR) and three single nucleotide variants and their haplotypes of FSH receptor (FSHR) genes determined by polymerase chain reaction (PCR) and DNA sequencing technique were compared between 29 partial and 34 complete suppressors.

Results: Baseline serum LH level was higher and serum LH as well as FSH level during the suppression phase was less suppressed in partial suppressors. Additionally, in a logistic regression analysis larger testis volume, higher serum FSH concentrations alone, or interaction of serum LH, FSH, testosterone and sperm concentrations were associated with degree of suppression. The distribution of polymorphisms of AR or FSH receptor genes did not differ between partial and complete suppressors. In cases with incomplete FSH suppression (FSH > 0.2 IU/L), the chances of reaching azoospermia were 1.5 times higher in the subjects with more than 22 CAG triplet repeats.

Conclusion: Partial suppression of spermatogenesis induced by 500 mg TU monthly injections is weakly influenced by hormonal and clinical features but not polymorphism in AR and FSHR genes.

Keywords: male contraception, genetic polymorphism, androgen receptor, CAG repeats, follicle stimulating hormone receptor, single nucleotide polymorphism, sperm concentration

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