Lactogenic hormone activity was first observed in bovine pituitary extracts by Stricker and Griiter in 1928, working in Bouin's laboratory in Strasbourg. Since that time prolactin has been shown to exist in anterior pituitary extracts of almost all vertebrate species investigated. Although its biology was extensively studied in many mammalian species, the existence of prolactin in the human was generally doubted, despite the positive evidence produced by such researchers as Pasteels. This can partly be explained by the fact that human growth hormone isolated in 1961, is itself a potent...