Melatonin

A. False Melanocyte-stimulating hormone is produced in the intermediate lobe of the pituitary; melatonin is produced mainly in the pineal gland.

B. True The necessary enzymes are in the pineal parenchymal cells.

C. False It has no role in regulation of human skin pigmentation.

D. True Melatonin secretion has a pronounced circadian rhythm, low during the day and high by night.

E. True Melatonin secreted in relation to prevailing conditions of light/darkness may adjust pituitary hormonal rhythms appropriately.