The Mechanism of Endocrine Control of Melanin Pigmentation*

IN RECENT years the relationship between hormones and the mechanism of pigmentation has come to the fore. In this report it will be shown that the pituitary gland elaborates a melanocyte-stimulating hormone (MSH) which affects melanin pigmentation in man. The “peculiar change” in skin color described by Addison in patients with adrenocortical insufficiency, the decreased pigmentation of panhypopituitarism, and the melasma of pregnancy seem to depend in large part upon the activity of MSH. Because the developments leading to this conclusion have involved many people and many aspects of research, it is worthwhile to review the historical background of this problem. In 1916 Smith and Allen, two biologists working independently, almost simultaneously reported that removal of the pituitary gland of tadpoles was followed by loss of skin color (1–4). Three years later Atwell showed that when tadpoles were immersed in pituitary extracts their skin became darker (5). Atwell, Smith, Swingle, and later Zondek found the active agent to be present in the intermediate lobe of the pituitary gland (5–9). Subsequently, Hogben, Winton, Waring, Landgrebe, Matthews, Zondek, Herrick, and Frieden added much to our understanding of the physiology of pituitary control of pigmentation in fish and amphibia (8–15).