Serum testosterone does not correlate with androgen tissue activity, and it is critical to optimize tools to evaluate such activity in males. Ultrasound measurement of bulbocavernosus muscle was used to assess the relationship between the number of CAG repeats in the androgen receptor and the bulbocavernosus muscle size; the changes in the number of CAG repeats over age were also evaluated. Transperineal ultrasound measurement of the bulbocavernosus muscle was also performed. Androgen receptor CAG repeats were determined by HPLC, and morning hormone levels were determined using immunoassays. Forty-eight men had CAG repeat analysis. Twenty-five were <30 years of age, mean 23.7 years (s.d. 3.24); 23 were >45 years of age, mean 53 years (s.d.: 5.58). The median CAG repeats was 21 (13–29). Bulbocavernosus muscle area was greater when the number of CAG repeats were <18 as compared to the number of CAG repeats >24 (P=0.04). There was a linear correlation between the number of CAG repeats and the bulbocavernosus muscle area R2 16% (P=0.01). In the 45-65 years old group, a much stronger negative correlation [R2 29% (P =0.01)] was noticed. In the 19-29 years old group, no such correlation was found [R2 4% (P =0.36)]. In older men, the number of CAG repeats increased with age [R2 32% (P =0.01)]. The number of CAG repeats in the androgen receptor correlates with the area of the bulbocavernosus muscle. Ultrasound assessment of the bulbocavernosus muscle is an effective surrogate to evaluate end-organ activity of androgens. The number of CAG repeats may increase with age.

Keywords: age; androgen activity; androgen receptor; androgen sensitivity; bulbocavernosus muscle; CAG repeats

Full Text | PDF | 中文摘要 |