Naughty Melatonin: How Mothers Tick Off their Fetus

Melatonin is a neurohormone synthesized and released from the pineal gland with both a daily and an annual rhythm controlled by the biological clock. The dual rhythm of melatonin is robust, reproducible, and, apart from light exposure at night, hardly altered. It is a strong and reliable clock output involved in the synchronization of circadian and seasonal functions. The physiological role of melatonin in the synchronization of seasonal function is long established, and recent studies are now deciphering the molecular and cellular mechanisms involved. However, the role of melatonin in the synchronization of daily functions is less clear and still in dispute because the doses required to observe significant effects are above physiological concentrations. Additionally, a few studies suggest that melatonin may be used by the mother to tell time to their fetus. In their paper published in this issue of Endocrinology, Torres-Farfan et al. (1) show that the clock in the fetal adrenal is indeed synchronized by melatonin pulses.