Melatonin-Related Hypogonadotropic Hypogonadism

Open Access
Publisher Website
Google Scholar
Abstract
THE secretion of melatonin from the pineal gland is linked to the light–dark cycle, being greater at night in all species, including humans, and it is pulsatile.1 In humans the peak nocturnal plasma melatonin concentration declines progressively with age, being highest in infants and prepubertal children and lowest in elderly people. Melatonin profoundly influences reproductive function in seasonally breeding mammals. One such species is the Syrian hamster, in which pinealectomy leads to sustained reproductive activity and in which appropriately timed injections of melatonin inhibit reproductive function.2 It is less clear whether melatonin has regulatory actions on the reproductive system in species that breed nonseasonally, such as humans. Some patients with hypothalamic hypogonadism have unusually high plasma melatonin concentrations,3 4 5 6 suggesting that increased pineal activity may be involved in the pathogenesis of this condition. Some boys with delayed puberty have elevated daytime plasma melatonin concentrations,7 and more than half of children with precocious sexual development have plasma melatonin concentrations lower than those of age-matched normal children.8 These data suggest that melatonin is important in pathologic conditions of the human reproductive system.