Pituitary pigmentary hormones. Relationship of melanocyte-stimulating hormone to lipotropic hormone.

Pituitary control of pigmentation has known for more than 60 years. Since 1969, beta-melanocyte-stimulating hormone (beta-MSH) has been accepted as the main pituitary pigmentary hormone in man. Its "constant companionship" with adrenocorticotrophic hormone (ACTH) has also been repeatedly demonstrated. Current investigations challenge both of these concepts. Human beta-MSH immunoreactivity has been shown to be actually due to beta-lipotropic hormone (beta-LPH), a larger molecule that within itself contains the entire amino acid sequence of beta-MSH. Human beta-MSH does not exist in vivo; it is merely an extraction artifact formed by enzymatic degradation of beta-LPH. It would appear likely that beta-LPH, not beta-MSH, is the constant companion of ACTH.