An evaluation of hormonal changes at puberty in man.

The pulsatile nature of the secretion of gonadotrophins, sex steroids and growth hormone are important in both the onset and maintenance of sexual maturation. The night-time is intimately related to the endocrine events which result in puberty, such that hormone measurements during the daytime have little meaning. This relationship between the night-time and gonadal function is not restricted to puberty but continues in adult life; the onset of the preovulatory LH surge occurs in the early hours of the morning. Girls seem more sensitive to small changes in GnRH concentrations than boys, which is why the physical signs of puberty appear slightly earlier in them. Low levels of oestradiol appear to assist growth hormone secretion, whereas higher levels of testosterone are required for the same effect. This probably explains the sex differences in the timing of the pubertal growth spurts.