Melatonin excretion in normal males and females: increase during puberty

Melatonin in chloroform extracts of timed overnight urine collections was measured by radioimmunoassay. Melatonin excretion was determined in 88 boys and 82 girls 9-16 yr of age, in 16 adult males, and throughout the menstrual cycle of one adult female. By succeeding age groups (9-10.9, 11-12.9, 13-14.9, and 15-16.9 yr) boys showed a progressive increase in mean +/- SD melatonin excretion from 3.0 +/- 1.3 ng/hr for the 9-10.9 yr age group to 9.8 +/- 2.8 ng/hr for the 15-16.9 yr age group. The girls' excretion increased for the 11-12.9 yr age group (9-10.9 versus 11-12.9 = 4.0 +/- 2.3 versus 6.1 +/- 2.7 ng/hr, p less than 0.005), plateaued for the 13-14.9 yr age group (5.8 +/- 3.3 ng/hr, p greater than 0.3), and decreased for the 15-16.9 yr age group (2.0 +/- 1.4 ng/hr, p less than 0.005). Subjects with initial signs of puberty as compared to prepubertal subjects had increased melatonin excretion (boys, 4.7 +/- 1.4 versus 2.4 +/- 0.9 ng/hr; girls 5.7 +/- 1.9 versus 2.4 +/- 0.9 ng/hr, p less than 0.005). Excretion of the adult males (1.6 +/- 1.1 ng/hr) was less (p less than 0.005) than that of boys of all age groups. At the time of menstrual bleeding melatonin excretion was elevated; peak excretion (15.5 ng/hr) occurred 3 days prior to the midcycle gonadotropin surge. Follicular phase (10.7 +/- 2.9 ng/hr) excretion was (p less than 0.005) greater than luteal phase (4.2 +/- 1.1 ng/hr) excretion. These data show that melatonin excretion increases when the initial signs of puberty are present. This finding is inconsistent with an inhibitory influence of melatonin on pubertal development. Gonadal function may influence melatonin secretion during puberty and melatonin may play a role in adrenarche.