Hiroshima University

Melatonin found to have broader effects in brain than once thought

Shift workers and travelers who pop melatonin pills to stave off drowsiness or jetlag have another reason to be cautious about taking the supplement, say Japanese and University of California, Berkeley, researchers. A new study shows that melatonin, a hormone available without prescription, has broader effects in the brain than once thought. In experiments on the Japanese quail, the researchers found that melatonin switches on a recently discovered hormone called gonadotropin inhibitory hormone (GnIH), which has been found to have the opposite effect to the key hormone priming the body for sex -- gonadotropin releasing hormone (GnRH). In birds, switching off GnRH causes the gonads -- testes and ovary -- to shrink as part of the birds' yearly cycle.