The relationship between anogenital distance and reproductive hormone levels in adult men

Purpose: Anogenital distance is a marker for endocrine disruption in animal studies in which decreased distance has been associated with testicular dysfunction. In this study we investigated whether anogenital distance was associated with reproductive hormone levels in adult men.

Materials and methods: A total of 116 men (mean age 36.1 ± 8.0 years) were evaluated at an andrology clinic in Houston. Anogenital distance (the distance from the posterior aspect of the scrotum to the anal verge) and penile length were measured using digital calipers. Testis size was estimated by physical examination. Linear regression was used to determine correlations between genital measurements and hormone levels.

Results: Anogenital distance (r = 0.20, p = 0.03) and penile length (r = 0.20, p = 0.03) were significantly associated with serum testosterone levels while total testis size was not (r = 0.17, p = 0.07). No relationship between genital length and luteinizing hormone, follicle-stimulating hormone or estradiol was identified. After adjusting for age the serum testosterone increased by 20.1 ng/dl (95% CI 1.8, 38.4; p = 0.03) for each 1 cm increase in anogenital distance. On multivariable models no statistically significant relationship existed between penile length and testosterone levels. Moreover men with hypogonadal testosterone levels (less than 300 ng/dl) had a significantly shorter anogenital distance compared to men with higher testosterone levels (31.6 vs 37.3 mm, p = 0.02).

Conclusions: Anogenital distance may provide a novel metric to assess testicular function in men. Assuming that anogenital distance at birth predicts adult anogenital distance, our findings suggest a fetal origin for adult testicular function.