Fall in nocturnal serum melatonin during prepuberty and pubescence.

Morning (7:30 AM to 10:00 AM) and nighttime (11:00 PM to 1:00 AM) serum melatonin concentrations were measured in 89 children, adolescents, and young adults. Morning levels (generally 0-20 pg/ml) did not change with sexual maturation or with age. Nighttime levels decreased significantly both with sexual maturation and with age. Nighttime serum melatonin fell from 195 +/- 24 pg/ml (mean +/- SEM) in prepubertal children younger than 7 years of age, to 119 +/- 23 pg/ml in prepubertal children aged 7 years or older, to 49 +/- 4 pg/ml in young adults (puberty stage V). Similarly, nocturnal serum melatonin levels fell from 210 +/- 35 pg/ml in the youngest age group (ages 1-5) to 133 +/- 17 in children aged 5-11 years and to 46 +/- 4 in young adults. Nocturnal plasma concentrations of luteinising hormone measured at various stages of puberty tended to vary inversely with those of melatonin (r = -0.35). Past difficulties in demonstrating a relation between gonadal maturation and human pineal function may have reflected the use of insufficiently sensitive or specific melatonin assays, or serum sampling only during daytime, or the initiation of sample collection when subjects were already too old.