Testicular response to human chorionic gonadotrophin in chronic hyperprolactinaemia

In order to evaluate the effect of hyperprolactinaemia on gonadal function in men, testicular stimulation by human chorionic gonadotrophin (hCG) (5000 IU/day, 3 consecutive days) was performed on 6 men with chronic hyperprolactinaemia and 6 control subjects. The following parameters were measured before and during the 4 consecutive days following the injections of hCG: the concentration in plasma of testosterone (T), oestradiol-17 beta (E2), dihydrotestosterone (DHT) and the urinary excretion of testosterone glucuronide (TG) and 5 alpha-androstane-3 alpha, 17 beta-diol glucuronide (3 alpha-Diol G). The rises in T, E2, DHT and the ratios of T/DHT and TG/3 alpha-Diol G were similar in both groups, but the rises in TG and 3 alpha-Diol G were lower in the hyperprolactinaemic group after hCG. There was no correlation between the response of T and the increment of E2 in either group. It is suggested that in men with chronic hyperprolactinaemia: 1) there is diminished testicular response to hCG; this could be due to chronic gonadotrophin deficiency or to a direct effect of hyperprolactinaemia on the testes, 2) there is no modulation of T synthesis through inhibition of aromatase activity and E2 secretion and 3) the 5 alpha-reduction of T is not deficient.