Effects of exogenous melatonin on pituitary hormones in humans

The effects of melatonin on physiological function remain unclear, although the therapeutic potential of melatonin is being increasingly recognized. T he aim of the present study is to investigate the effects of exogenous mela tonin on the spontaneous release of pituitary hormone in humans. A double b lind placebo-controlled protocol was designed to examine 12 adult healthy v olunteers and 12 sleep disorder patients who have been treating with low do ses of melatonin for 1 year. Either exogenous melatonin or placebo of 1 mg was given at 09:00 hours, followed by the collection of blood samples every 20 min for 4 h. Each blood sample was examined for levels of serum melaton in, PRL, LH, FSH, GH and TSH. LH levels were higher in sleep disorder patie nts compared with the healthy volunteers. In other pituitary hormones, ther e were no significant difference between healthy adults and sleep disorder patients. In all subjects, PRL levels were stimulated by acute administrati on of 1 mg of exogenous melatonin, while the levels of other pituitary horm ones were not affected. These results suggested that exogenous melatonin ca n affect the spontaneous release of LH and PRL in humans. In addition, we d emonstrated that 1-year oral melatonin treatment did not affect the respons es to the acute administration of melatonin.