Melatonin metabolite excretion during childhood and puberty.

Daily urinary excretion of conjugated 6-hydroxymelatonin, the major metabolite of the pineal hormone melatonin, has been determined in 54 boys and 47 girls (aged 3-16 yr) and 20 normal adults to determine whether a change in melatonin production is seen during the maturation of reproductive function in humans. There was no correlation between daily excretion rates and age in children, and the excretion rates were similar to those in adults. In addition, children of all ages had normal circadian patterns of 6-hydroxymelatonin excretion from the earliest age tested. A significant increase in 6-hydroxymelatonin excretion was observed at the time of the onset of breast development (Tanner stage II) in girls. No similar difference was seen during puberty in males. The significance of this difference in Tanner II girls is not known.