Apr 2012 – by R. Schenken, MD
Prolactin is secreted by the lactotroph cells in the pituitary gland. Elevations in serum prolactin usually result from conditions that cause hypersecretion of prolactin by the lactotrophs. These conditions include: (1) physiologic causes such as stress, nipple stimulation, sleep, exercise, coitus, pregnancy and lactation; (2) pathologic causes including (a) hypothalamic-pituitary stalk damage due to trauma, radiation, Rathke’s cyst, infiltrative diseases and parasellar tumors; (b) pituitary disorders such as prolactinomas, acromegaly, and macroprolactimemia; (c) systemic disorders such as primary hypothyroidism; chest wall injury due to trauma, surgery, herpes zoster; chronic renal failure with decreased clearance of prolactin, cirrhosis, malignancies such as renal and lung cancer; (3) pharmacologic causes due to some antipsychotics, gastric motility drugs, antihypertensives, dopamine receptor blockers, opiates, and H2 antihistamines; and (4) idiopathic.
The clinical manifestations of hyperprolactinemia in premenopausal women include oligomenorrhea, amenorrhea, infertility, galactorrhea, headaches and visual disturbances. In general, these symptoms correlate with the magnitude of the hyperprolactinemia. A serum prolactin concentration above 20-25 ng/mL is considered abnormally high in most laboratories.
The evaluation should include a history of medications, pregnancy, headache, visual symptoms, hypothyroidism symptoms, and renal/liver disease. The physical examination should be directed for signs of hypothyroidism, hypogonadism, visual field loss, and looking for chest wall injury.
Laboratory tests should include a prolactin and TSH. An MRI of the sella turcica is required to diagnose a micro/macroadenoma or a mass lesion in the hypothalamic-pituitary region. Microadenomas are defined as prolactinomas less the 10 mm and macroadenomas are those greater than 10 mm.
Symptomatic patients with hyperprolactinemia may be treated with bromocriptine or cabergoline. Monitoring with prolactin levels is necessary to adjust medication dosages. Repeat MRIs are dependent on the clinical situation. Treatment during pregnancy is usually limited to symptomatic patients and those with macroadenomas.
Case Study: A 28 year-old G1P1complains of oligoamenorrhea. She is not pregnant and is not taking medications. Evaluation includes a prolactin of 60 ng/ml, normal TSH, and an MRI of the brain is normal. This is most likely the result of macroprolactinemia, idiopathic prolactinemia, or a microadenoma that is too small to be seen on imaging. Macroprolactinemia is due to large polymeric forms of prolactin and circulating anti-prolactin autoantibodies. These forms of prolactin are less biologically active, consequently fewer patients are symptomatic and prolactinomas are present is only about 10-20%.