Evaluation of human chorionic gonadotropin stimulation tests in prepubertal and early pubertal boys.

We evaluated the diagnostic significance of single versus repeated human chorionic gonadotropin (hCG) stimulation of testicular steroidogenesis in 25 boys (10 prepubertal group A; 15 early pubertal, group B) with suspected hypogonadism. All subjects received a single injection of hCG (5000 U/1.7 m2) and 1 month later, three repeated injections of 1500 U, one each on alternate days. In 19 out of the 25 boys, testosterone increased normally in both tests: from 20 +/- 6 to 156 +/- 82 ng/dl and from 107 +/- 105 to 615 +/- 293 ng/dl, following a single hCG injection, and from 30 +/- 19 to 439 +/- 298 ng/dl and from 94 +/- 55 to 826 +/- 272 ng/dl, following repeated injections in groups A and B, respectively. The difference between the tests was significant (P < 0.01). Conclusion. Single hCG injection used as a screening test in the evaluation of hypogonadism is conclusive when positive. Only when the initial test is negative may a repeated test help establish the diagnosis.