Brandon Bankowski

Dopamine agonist therapy for hyperprolactinemia

Prolactin Prolactin is a 199-amino acid protein synthesized within and secreted from lactotropes in the anterior pituitary gland. Numerous biologic actions have been ascribed to this protein, but it is most widely known for its stimulatory actions upon the milkproducing cells of the breast. After expulsion of the placenta after childbirth, breast milk letdown occurs as a consequence of the decline in levels of estradiol, estrone, estriol, and progesterone. Breast milk production begins and continues in response to exposure to prolactin secreted as a result of nipple stimulation during breastfeeding. Anovulation accompanied by amenorrhea usually exists during breastfeeding and may last for weeks or months depending upon the duration, frequency, and intensity of the nipple stimulation. The presumed cause of anovulation and amenorrhea is the suppression of gonadotropin release resulting either from the inhibition of GnRH release by stimulation of prolactin receptors or increased dopamine turnover in the hypothalamus caused by prolactin. The pituitary hormone, prolactin, was discovered in the rabbit in 1928. After its discovery, prolactin was found to be involved in milk production, as demonstrated by its stimulatory activity on milk production from the pigeon crop sac. Prolactin was also found to be involved in maintaining corpus luteum production of progesterone in the rat. The existence of a human prolactin molecule was long suspected but not identified until 1971, by Hwang et al.