NOCTURNAL BIOACTIVE FSH PULSES ARE EVIDENT IN PRE (PERI) PUBERTAL BOYS

Secretion of both LH and FSH is pulsatile and maximal during the night in early peripubertal boys. To evaluate the pulsatile pattern of bioactive FSH (B-FSH), we assessed serum concentrations of B-FSH in four Tanner Stage I boys with constitutional growth delay (mean age 15y 3m, mean bone age 12y 6m) and compared their data to previously published data from 6 Tanner Stages II-III pubertal boys (Hassing et al, JCEM, 1990, 70:1082). Each of the four boys had a 12 h overnight blood sampling (every 20 min) followed by administration of 1μg/kg nafarelin sc. Serum I-LH and I-FSH were measured by RIA and B-FSH was measured by the rat Sertoli cell aromatase induction assay using hLH-13 and hFSH-13 standards and expressed as ng/ml. The mean serum I-LH, I-FSH and B-FSH were 0.63±0.06, 0.40±0.15 and 1.8±0.2 ng/mL (p<0.05, B vs I FSH). B-FSH pulse frequency was similar to I-LH pulse frequency (0.43±0.1 and 0.43±0.05 pulses/boy/h) and to previously published data in mid pubertal boys. ΔI-LH release was 3.3±0.7, ΔI-FSH was 2.4±0.6 and ΔB-FSH was 4.2±1.4 ng/mL. We conclude that during the peripubertal period in boys, serum B-FSH is secreted in a pulsatile manner and the concentrations exceed those of serum I-LH or I-FSH.