It is known that in the absence of light stimulation through the retina, melatonin is secreted by the pineal gland. Melatonin has a recognised anti-gonadotrophic effect. It also plays a role in regulating the 24 hour and seasonal rhythms. In the pituitary gland it inhibits the secretion of LH and therefore indirectly has suppressing effect in the regulation of the reproductive system. It may also have some direct effect on the reproductive system by inducing the secretion of progesterone in the grainy layer of the ovaries in vitro. In addition there is an increased sensitivity to exogenous melatonin by receptors for melatonin which is at it highest peak in the afternoon. Further study of these phenomena is needed to determine if melatonin is effective enough to be used in the regulation of the reproductive system (there may be a potential for its use in birth control).

Keywords: LHRH, FSH, LH, Melatonin