Melatonin regulates sleep-wake cycles, puberty timing, gonadal function, and bone mass.

“So melatonin is regulating how awake or asleep we are. It tends to make us more asleep, incidentally. It's regulating our timing of puberty, and it's regulating how our gonads, the testes and ovaries, function, even in adulthood, to some extent. And it's regulating bone mass.”