The effects of oral melatonin on skin color and on the release of pituitary hormones.

We studied the effects of prolonged ingestion of melatonin, 1 g per day, on skin color and the serum levels of pituitary hormones in 5 human subjects with hyperpigmented skin. Melatonin lightened hyperpigmented skin of one patient with untreated adrenogenital syndrome, but had no effect on three patients' skin with idiopathic hyperpigmentation and one patient with treated Addison's disease. Melatonin appeared to depress the level of luteinizing hormone (LH) in serum and may have inhibited in some patients the release of growth hormone from the pituitary gland after stimulation by stress or L-dopa. The subjects all noted increased drowsiness but through studies on the eyes, liver, kidneys, and bone marrow revealed no other evidence of toxicity.