Plasma testosterone response to short-term human chorionic gonadotropin administration in men with follicle-stimulating hormone suppressed by exogenous estrogen.

In order to investigate the role of FSH in Leydig cell function, six men were given four daily injections of HCG (4,000 IU) while receiving oral ethinyl estradiol. The peak testosterone levels in these subjects were contrasted to the results obtained in seven men who received HCG without additional exogenous steroid treatment. Urinary and plasma FSH was suppressed to 26% and 50%, respectively, of basal values by the estrogen treatment. Peak plasma testosterone determinations following HCG did not differ in the two groups of subjects. Additionally, an early pubertal boy had a normal HCG-induced testosterone rise while his urinary FSH was suppressed by estradiol to lower than prepubertal levels. The data indicate the short-term FSH suppression does not alter testicular responsivity to short-term HCG administration. A role for FSH in Leydig cell testosterone production in men has yet to be demonstrated.