Prolactin exerts many physiologic functions, perhaps the most prominent of which is inducing lobuloalveolar growth of the mammary gland, along with stimulation of lactogenesis or milk production after giving birth. The majority of prolactinomas contains only lactotroph cells and produce prolactin in excess. The major mechanism is a threefold increase in prolactin secretion, and a one-third decrease in metabolic clearance rate. Oligomenorrhea, amenorrhea, galactorrhea, infertility, hot flashes, vaginal dryness, headaches, and visual changes are clinical manifestations of hyperprolactinemia in premenopausal women. Women who have lactotroph microadenoma causing hyperprolactinemia and hypogonadism and cannot tolerate or do not respond to dopamine agonists and do not want to become pregnant can be treated with estrogen and progestin. Cabergoline is the most effective of the dopamine agonists but is the most expensive. Intravaginal administration of dopamine agonists reduces their side effects.

Hyperprolactinemia has a detrimental effect on fertility both in women and men, leading to galactorrhea anovulation, amenorrhea, oligomenorrhea, impotence, gynecomastia, and low semen profile. Men with hyperprolactinemia not only show abnormal semen analysis but also abnormal histological structure of the testicles with distorted seminiferous tubules and abnormal sertoli cells. Many physiological and or pathological changes involving lactotroph cells can result in hyperprolactinemia. The majority of prolactinomas contains only lactotroph cells and produce prolactin in excess. Antihypertensive drugs like methyldopa and reserpine increases prolactin secretion. A dopamine agonist drug should usually be the first line of treatment for patients with hyperprolactinemia of any cause including lactotroph adenomas of all sizes. Bromocriptine, cabergoline, pergolide are the available dopamine agonists to treat hyperprolactinemia. Dopamine agonists decrease prolactin secretion and reduce the size of the lactotroph adenoma in more than 90 percent of patients. Surgical and radiation treatment are also useful.