Gonadotrophin and growth hormone secretion throughout puberty.

The secretion patterns of gonadotrophin and growth hormone (GH) were investigated in normal healthy children at different stages of pubertal development. The plasma levels of luteinizing hormone (LH) and GH were measured at 10-minute intervals from 12.00 h to 18.00 h and from 24.00 h to 06.00 h using immunoradiometric assays. The levels of follicle-stimulating hormone (FSH) and testosterone were measured hourly. In young prepubertal girls and boys LH was undetectable during the day or night. In children of pubertal chronological age, in whom secondary sexual characteristics had not appeared (stage 1 onset), LH was detectable during the night only. With the progression of puberty there was a gradual increase in the secretion of LH, resulting from increases in both the frequency and amplitude of LH pulses. There was a clear increase in the secretion of FSH during day and night from stage 2 onwards. The secretion of GH also increased with the progression of puberty, due to an increase in pulse amplitude. The increase in GH secretion did not appear to be related to the increase in LH secretion, but rather to changes in the sex steroids.