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.