Amplification of pulsatile LH secretion by exogenous melatonin in women

The effect of melatonin on pulsatile LH secretion was investigated in early follicular phase women (days 2-5). During two consecutive days, at 0800 hrs., subjects received placebo or oral melatonin in a random double-blind fashion. Two doses of melatonin were used; 100 mg single dose (N = 6) or 2.5 mg in three divided doses (N = 5), (1 mg at 0800 hrs., 0.75 mg at 1000 and 1200 hrs.). Blood samples were collected every 10 minutes, between 0900-1700 hrs. Compared with placebo, melatonin administration augmented LH pulse amplitude (p less than 0.01) without changing LH pulse frequency. The integrated LH secretion was significantly increased (p less than 0.01) after melatonin, independent of doses administered. Serum FSH and ovarian steroids were not altered. It is concluded that exogenous melatonin enhances LH pulse amplitude in women, without modifying FSH and ovarian steroid levels.