Evaluation of leydig-cell function in normal prepubertal and pubertal boys

Plasma levels of testosterone (T), estrone (E1) and estradiol (E2) have been studied in 115 normal boys 5–19 years old and related to pubertal stages. The significance of pubertal changes is greater for T than for E1 and E2, and the increase of T begins earlier than the increase of E2. Response to HCG, 3 × 1500 IU every other day, has been studied in 61 of these subjects. The increase of testosterone from basal to post-stimulatory levels (ΔT) goes up at the beginning of puberty but does not change further. ΔE1 does not increase significantly during puberty. ΔE2 increases at late puberty. All normal prepubertal boys had a definite response of T to HCG, peak level being at least 1.60 ng/ml. The number of injections of HCG and the duration of the stimulation are more important than the doses injected to obtain maximal Leydig-cell stimulation in prepubertal children.