Correlation of Acute and Chronic Increases in Serum Gonadal Steroid Levels After Administration of Human Chorionic Gonadotropin

Abstract

The standard method for assessment of Leydig cell reserve requires determination of the increase in serum testosterone levels after several days of human chorionic gonadotropin (hCG) administration. To determine whether a shorter period of hCG administration would yield useful results, we measured the increases in serum testosterone and 17-hydroxyprogesterone levels 2 hours after an intramuscular injection of 4000 units of hCG (short hCG test) and compared these results with the increase in serum testosterone after 96 hours of hCG administration (standard hCG test). By 2 hours after the initial hCG injection, the control group showed significant percentage increases (mean ± standard error) over basal levels for serum testosterone (24% ± 4%; P < 0.001) and serum 17-hydroxyprogesterone (68% ± 11%; P < 0.001). The percentage increase in serum testosterone during the standard hCG test correlated with both the acute percentage increase in serum testosterone (r = 0.694, P < 0.001) and the acute percentage increase in serum 17-hydroxyprogesterone (r = 0.672, P < 0.001). Subjects with primary testicular failure showed responses to the short and standard hCG test which, when expressed as percentage increase, greatly overlapped the control values. Subjects with hypothalamic-pituitary dysfunction tended to have minimal increases in testosterone during the short hCG test and exaggerated increases in testosterone, expressed on a percentage basis, during the standard hCG test. We conclude that (1) significant increases in serum testosterone and 17-hydroxyprogesterone can be detected 2 hours after an intramuscular injection of hCG (short hCG test); (2) responses to the short hCG test correlate with the responses to the standard hCG test; and (3) control subjects show great variability in responses to both short and standard hCG tests, and neither the short nor the standard hCG test clearly separates subjects with disorders of the hypothalamic-pituitary-testicular axis from control subjects.