Melatonin and sex hormone interrelationships - A review

Melatonin, the main hormone secreted by the pineal gland at night, plays a major role in regulating reproductive physiology in seasonal breeders and i nfluences the age of sexual maturation in laboratory rodents. In humans the se relationships are less clear. Evidence supporting a melatonin-reproducti ve hormone relationship relies on findings of abnormal melatonin secretion in disorders of the reproductive system and on pathologies of the pineal gl and which are associated with clinical abnormalities of the reproductive ho rmones. Normal melatonin rhythms are closely related to those of the reprod uctive hormones during infancy and reciprocally correlated during puberty. The demonstration of melatonin receptors in the brain and in reproductive o rgans, together with the localization of sex hormone receptors in the pinea l gland, further strengthen these relationships. However, it is not yet cle ar that these correlations are functionally related, as data on the antigon adal effects of exogenous melatonin on the reproductive hormones are not co nclusively established.