Pituitary Tutorial—Prolactinoma
Prolactinomas, AKA prolactin-secreting pituitary tumors.
Prolactinomas are probably the most common of the known pituitary tumors.
We will discuss:
- History and physical examination
- Laboratory and imaging tests which help in diagnosis
- Differential diagnosis of hyperprolactinemia
- Treatment of this tumor
- We will also mention some in the treatment of prolactinomas
History and Physical Examination
Prolactinomas typically present with two syndromes:
- a young woman with galactorrhea and amenorrhea (a hormone-secreting syndrome),
- an older man with fatigue and visual changes (a mass-effect syndrome).
Galactorrhea-amenorrhea
These young women usually present to their OB-GYN doctors with inability to conceive children. On further questioning, they are noted to have irregular or absent menstrual periods for months to years. Physical examination reveals galactorrhea often, but not always. The visual field examination of these women is typically normal.
Fatigue and visual changes
These typically older men present with lassitude, decreased libido, and variable visual complaints. On examination, they may have loss of body hair, and bitemporal hemianopia (NOTE: it is exceedingly rare for a person to
complain of bitemporal hemianopia--our field of binocular vision is too wide).
Laboratory and imaging studies
Laboratory studies of use include a prolactin level, which is typically elevated in these patients.
Imaging studies best performed is the MR with and without gadolinium enhancement. Really, folks, the days of the CT scan for diagnosing pituitary tumors are over. MR scanning, which drops bone out of the image, shows the tumor and its surrounding structures with exquisite detail. Small tumors are best appreciated on MR. You don't even catch any X-rays, they do it with magnets (really).
Differential diagnosis of hyperprolactinemia
Hyperprolactinemia can be caused by:
- Pregnancy
- Phenothiazines, butyrophenones, antidepressants
- Renal failure
- Cirrhosis
- Primary hypothyroidism
- Pituitary stalk compression
Prolactin levels for all of these problems rarely exceed 150 ng/ml. Also, there is a (very) rough correlation between pituitary tumor size and expected prolactin level: a 10 mm tumor should produce a serum prolactin of around 100 ng/ml. This rule becomes useful when you have, e.g., a 30 mm tumor and a prolactin level of 50 ng/ml: think of a nonsecreting tumor here, not prolactinoma.
Treatment of prolactinomas
The mainstay of prolactinoma treatment is oral administration of dopamine agonists, in the United States in 1999: bromocriptine, cabergoline, or pergolide. These medications are safe and 80-90% effective, with treatment limited most often by nausea. They may be given to patients with a large prolactinoma with safety. They should not be given to a woman for the first 6 months post-partum, because they increase her chance of stroke or MI during this period.
Only rarely will a prolactinoma patient require surgery, often a woman with a macroadenoma who has failed bromocriptine therapy during pregnancy.
Controversies in prolactinomas
Among the controversies in the treatment of prolactinomas are:
- Should a pregnant woman continue on her bromocriptine through pregnancy?
- Should surgery be the primary treatment for microadenomas secreting prolactin?
- Should radiation therapy be used to treat prolactinomas?
- If dopamine agonist therapy fails due to side-effects (e.g. nause), what should be the next step in therapy?
- Should prolactinomas with mildly elevated prolactins (40-70 ng/ml) even be treated at all?
Such questions provide grist for controversies during endocrinological and neurosurgical meetings.
