Abstract
Pituitary control of pigmentation has been known for more than 60 yr. Since 1969, .beta.-melanocyte-stimulating hormone (.beta.-MSH) has been accepted as the main pituitary pigmentary hormone in man. Its constant companionship with ACTH has been repeatedly demonstrated. Current investigations challenge these concepts. Human .beta.-MSH immunoreactivity was 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.