Dissociated responses of plasma testosterone and estradiol to human chorionic gonadotropin in adult men.

Plasma testosterone (T), dihydrotestosterone (DHT) and estradiol (E2) were determined by radioimmunoassay in 10 normal males receiving hCG im 5000 IU on days 1, 2 and 3. The mean increase of plasma steroid on days 2, 3 and 1, respectively, was: 1.42, 1.79 and 1.87 times for T; 1.17, 1.56 and 1.49 times for DHT; 4.04, 3.29 and 2.33 times for E2. While T was still significantly increasing from day 2 to day 4, E2 significantly decreased. A positive correlation (P less than 0.01) was found between the basal T and the E2 peak after hCG, suggesting a release of E2 from a storage compartment in the testis. No significant change of either steroid was detected 4 h after the first hCG injection. In 6 cases of primary male hypogonadism, the mean basal values of T to hCG was defective, despite considerable individual variations. In 14 males with gonadotropin deficiency, basal values of T and E2 were very low; the T response to hCG ranged from undetectable to dramatic, and was correlated with the degree and duration of previous exposure to gonadotropin; and impaired response of E2 in all cases porvides a better estimate of the actual gonadotropin deficiency.