Melatonin does not suppress the pituitary luteinizing hormone response to luteinizing hormone-releasing hormone in men.

The effect of an iv melatonin infusion on the pituitary LH response to LHRH was studied in five young men. Melatonin (30 micrograms/min; total dose, 7.2 mg) was infused for a 4-h period, 2 h before and 2 h after a LRH stimulation (single iv 150-microgram dose). Each subject's control response to LRH was obtained previously. During the melatonin infusion, supraphysiological concentrations of melatonin (20 times) were documented using a specific RIA. All five subjects had a LH rise after LRH stimulation, and this response was not affected by the melatonin infusion. These results indicate that an acute constant infusion of a pharmacological amount of melatonin does not suppress LRH-induced LH release from the pituitary in men. In addition, no change in sleepiness and behavior was found.