Prolactin

Prolactin (PRL), also known as lute tropic hormone, is a protein best known for its role in enabling mammals (and birds), usually females, to produce milk. It is influential in over 300 separate processes in various vertebrates, including humans. Prolactin is secreted from the pituitary gland in response to eating, mating, estrogen treatment, ovulation and nursing. It is secreted heavly in pulses in between these events. Prolactin plays an essential role in metabolism, regulation of the immune system and pancreatic development.In mammals, prolactin is associated with milk production; in fish it is thought to be related to the control of water and salt balance. Prolactin also acts in a cytokine-like manner and as an important regulator of the immune system. It has important cell cycle-related functions as a growth-, differentiating- and anti-apoptotic factor. As a growth factor, binding to cytokine-like receptors, it influences hematopoiesis and angiogenesis, and is involved in the regulation of blood clotting through several pathways. The hormone acts in endocrine, autocrine and paracrine manner through the prolactin receptor and numerous cytokine receptors.