Normal control of prolactin secretion and how it is altered in prolactin secreting tumors?
Multiple factors affect prolactin secretion. However, the principal influence on prolactin secretion is tonic inhibition by dopamine input from the hypothalamus. Dopamine interaction with receptors of the D2 subtype on pituitary lactotroph membranes activates the inhibitory G-protein, leading to decreased adenylate cyclase activity and decreased levels of cyclic adenosine monophosphate (cAMP). In prolactin-secreting pituitary adenomas, a monoclonal population of prolactin-producing cells escapes the normal physiologic input of dopamine from the hypothalamus, apparently by acquiring a peripheral blood supply. In almost all cases, responsiveness to a pharmacologic dose of dopamine is maintained.