A simple hCG stimulation test for normal and hypogonadal males.

A simple human chorionic gonadotropin (hCG) test to measure Leydig cell function is described. Plasma testosterone was measured on two occasions, once before intramuscular injection of 10,000 IU of hCG and again four days later. Preliminary tests in 10 adult males showed a maximal increase in plasma testosterone between the third and fifth day that was confirmed in a further 20 normal subjects when measured once on the fourth day. Except for 2 patients with hypospermatogenesis, 24 showed a good response and the mean increase was comparable with that in normal males. Nineteen patients with Klinefelter's syndrome usually had lower basal levels and showed a poor response, with the exception of six patients in whom there were moderate but definite increases. Twelve patients with hypogonadotropic hypogonadism had basal testosterone concentrations below 1 ng/ml and eight responded poorly to hCG stimulation. However, four patients showed a moderate but definite response.