Prolactin
Prolactin is a polypeptide secreted by the lactotropic cells of the anterior pituitary. It initiates and maintains lactation and development of the mammary gland. There are several circulating forms: monomers, dimers, aggregates and glycosylated forms. Its serum levels exhibit remarkable diurnal rhythm. The determination of prolactin levels can be used as an aid in diagnosis of infertility, impotence, pituitary tumors and prolactinomas and as an aid in monitoring of prolactinomas.