melanocyte-stimulating hormone

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A hormone secreted by the pituitary gland that regulates skin color in humans and other vertebrates by stimulating melanin synthesis in melanocytes and melanin granule dispersal in melanophores.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun biochemistry Any of a class of peptide hormones released by the pituitary gland that are involved in regulating the production of melanin.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a hormone secreted by the anterior pituitary gland that controls the degree of pigmentation in melanocytes