Prolactinoma is a condition in which a noncancerous tumor (adenoma) of the pituitary gland in your brain overproduces the hormone prolactin. The major effect is decreased levels of some sex hormones — estrogen in women and testosterone in men.
Although prolactinoma isn’t life-threatening, it can impair your vision, cause infertility and produce other effects.
Most prolactinomas occur in women between 20 and 34 years old, but can occur in both sexes at any age. The disorder is rare in children.
There may be no noticeable signs or symptoms from prolactinoma. However, signs and symptoms can result from excessive prolactin in your blood (hyperprolactinemia) or from pressure on surrounding tissues from a large tumor. Because elevated prolactin can disrupt the reproductive system (hypogonadism), some of the signs and symptoms of prolactinoma are specific to females or males.
In females, prolactinoma can cause:
- Irregular menstrual periods (oligomenorrhea) or no menstrual periods (amenorrhea)
- Milky discharge from the breasts (galactorrhea) when not pregnant or breast-feeding
- Painful intercourse due to vaginal dryness
- Acne and excessive body and facial hair growth (hirsutism)
In males, prolactinoma can cause:
- Erectile dysfunction
- Decreased body and facial hair
- Uncommonly, enlarged breasts (gynecomastia)
In both sexes, prolactinoma can cause:
- Low bone density
- Reduction of other hormone production by the pituitary gland (hypopituitarism) as a result of tumor pressure
- Loss of interest in sexual activity
- Visual disturbances
Women tend to notice signs and symptoms earlier than men do, when tumors are smaller in size, probably because they’re alerted by missed or irregular menstrual periods. Men tend to notice signs and symptoms later, when tumors are larger and more likely to cause headache or vision problems.
A doctor will test for prolactin blood levels in women with unexplained milk secretion (galactorrhea) or irregular menses or infertility, and in men with impaired sexual function and, in rare cases, milk secretion. If prolactin is high, a doctor will test thyroid function and ask first about other conditions and medications known to raise prolactin secretion. The doctor will also request a magnetic resonance imaging (MRI), which is the most sensitive test for detecting pituitary tumors and determining their size. MRI scans may be repeated periodically to assess tumor progression and the effects of therapy. Computed Tomography (CT scan) also gives an image of the pituitary, but it is less sensitive than the MRI.
In addition to assessing the size of the pituitary tumor, doctors also look for damage to surrounding tissues, and perform tests to assess whether production of other pituitary hormones is normal. Depending on the size of the tumor, the doctor may request an eye exam with measurement of visual fields.
The goal of treatment is to return prolactin secretion to normal, reduce tumor size, correct any visual abnormalities, and restore normal pituitary function. As mentioned above, the impact of stress should be ruled out before the diagnosis of prolactinoma is given. Exercise can significantly reduce stress and, thereby, prolactin levels. In the case of very large tumors, only partial reduction of the prolactin levels may be possible.
Dopamine is the chemical that normally inhibits prolactin secretion, so doctors may treat prolactinoma with bromocriptine, cabergoline or Quinagolide drugs that act like dopamine. This type of drug is called a dopamine agonist. These drugs shrink the tumor and return prolactin levels to normal in approximately 80% of patients. Both have been approved by the Food and Drug Administration for the treatment of hyperprolactinemia. Bromocriptine is associated with side-effects such as nausea and dizziness and hypotension in patients with already low blood pressure readings. To avoid these side-effects, it is important for bromocriptine treatment to start slowly.
Surgery should be considered if medical therapy cannot be tolerated or if it fails to reduce prolactin levels, restore normal reproduction and pituitary function, and reduce tumor size. If medical therapy is only partially successful, this therapy should continue, possibly combined with surgery or radiation treatment.
The results of surgery depend a great deal on tumor size and prolactin level. The higher the prolactin level the lower the chance of normalizing serum prolactin. In the best medical centers, surgery corrects prolactin levels in 80% of patients with a serum prolactin less than 250 ng/ml. Even in patients with large tumors that cannot be completely removed, drug therapy may be able to return serum prolactin to the normal range after surgery. Depending on the size of the tumor and how much of it is removed, studies show that 20 to 50% will recur, usually within five years.