[Current concepts on prolactin physiology: molecular variants and mechanisms of action]

Prolactin is a polymorphic hormone with multiple biological functions. The versatility in the actions of prolactin depends on its structural polymorphism and perhaps on the feasibility of prolactin to be converted into different bioactive forms. In this review we attempt to summarize information concerning the synthesis, structure and mechanisms of action, including the heterogeneous nature of prolactin and its possible physiological significance in humans.