THE DISCOVERY OF HUMAN PROLACTIN - A VERY PERSONAL ACCOUNT

Although prolactin was discovered in the early 1930's in sheep, cows, birds etc., no human form had been because it was thought to be identi cal to human growth hormone (HGH). In fact, prior to 1970, most endocr inologists doubted human prolactin even existed. Prolactin-like effect s could be demonstrated from a homogenate of human pituitary but attem pting to purify it identified only growth hormone. Independent histolo gical studies had identified prolactin-secreting ''pregnancy cells'' f uelling the conviction that prolactin was a distinct and separate pitu itary hormone. A search was begun for prolactin through protein synthe sis studies using pituitaries from pregnant and postpartum monkeys. Pr oteins obtained in a radioactive peak were similar to, but not identic al with, growth hormone by molecular weight and electrophoretic mobili ty. The hypothesis that the unknown protein peak represented synthesis of prolactin rather than growth hormone proved correct. Evidence was then obtained confirming that in the human pituitary prolactin and gro wth hormone synthesis could be distinguished using antibodies to human growth hormone or to sheep prolactin. Human prolactin purified from p ituitary glands using immunological tools capable of distinguishing be tween the two hormones provided ultimate proof of a separate and disti nct human prolactin, a hormone which has its major impact today in end ocrinology and reproductive medicine. This discovery represented an ex citing and truly international collaborative effort.