Growth hormone secretion patterns in relation to LH and testosterone secretion throughout normal male puberty

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Abstract
Pulsatile growth hormone secretion patterns were studied in relation to LH and testosterone release in 30 healthy prepubertal boys and 2 adult men. Plasma GH was measured every 10 min, plasma LH and testosterone every hour. Night-time GH secretion parameters were 2-3 times higher than daytime values. During daytime, mean GH level and the fraction of GH in pulses increased from Tanner stage G2 to G4 (p = 0.01); during night-time these parameters increased as well (P .ltoreq. 0.1) and decreased from stage G5 to adulthood (p = 0.05). GH pulse number did not increase; the number of high-amplitude (> 8 .mu.g/l pulses, however, increased from stage G2 to G4 (p = 0.05) during the day. Height velocity correlated with the number of high pulses during day and night .tau. = 0.39, p < 0.003). From stage G2 to G3 significant correlations were observed between nocturnal testosterone levels and GH secretion parameters (.tau. - 0.53 - 0.57), in contrast to nocturnal LH levels. It is concluded that during puberty 1. GH secretion increases as a result of an increased pulse amplitude; 2. there is no consistent correlation between GH and LH levels; 3. increasing nocturnal; testosterone levels are correlated with the increasing GH secretions; therefore GnRH does not seem to influence GH secretion directly, but an indirect effect via testosterone is more conceivable, and 4. height velocity is correlated with the number of high GH pulses.