Prolactin

Abstract
PROLACTIN was discovered in 1928, as a lactogenic substance present in extracts of the pituitary gland of the cow. However, it is only since 1970 that this hormone has been definitely identified and measured in human blood. The long delay in its recognition as a human hormone came about because human growth hormone, unlike non-primate growth hormones, has strong intrinsic lactogenic potency, which obscured detection of the small amounts of prolactin present in human pituitary extracts. In 1970, by means of a sensitive bioassay, prolactin was shown to be present in human blood as a substance immunologically distinct from growth . . .