Pituitary Center

Diagnosis and Treatment of Prolactinoma

A Prolactinoma is the most common type of pituitary tumor. Prolactin stimulates the breast to produce milk during pregnancy. After delivery of the baby, a mother's prolactin levels fall unless she breast feeds her infant. During nursing, prolactin levels rise to maintain milk production. 

A Prolactinoma is a benign tumor of the pituitary cells that produce prolactin, resulting in high levels of prolactin in the blood (hyperprolactinemia).

Treatment at Stanford

Patients can receive an evaluation and treatment for prolactinoma at the Stanford Pituitary Center.

Signs & Symptoms

Symptoms of prolactinoma are caused by hyperprolactinemia or by pressure of the tumor on surrounding tissues.

Women

  • In women, hyperprolactinemia often cause changes in menstruation and infertility.
  • Some women may lose periods altogether (amenorrhea), and others may have irregular or infrequent menstruation.
  • Women who are not pregnant or nursing may begin producing breast milk (called galactorrhea). Some women may experience a loss of libido (interest in sex).
  • Patients with large pituitary tumors (macroadenomas, greater than 10 mm) may also have low levels of the other pituitary hormones (called hypopituitarism) because of pressure of the tumor on the normal gland.  Therefore, it is important for the physician to measure the other pituitary hormones as well.  Macroadenomas, if compressing the optic nerves, could cause loss of peripheral vision as well.

Women with hyperprolactinemia and amenorrhea may have an increased risk for osteoporosis (bone loss).  In amenorrhea, the ovaries are producing inadequate amounts of estrogen, which increases the risk for osteoporosis. It is important for women  with a history of amenorrhea to have bone density measurements performed, even after hyperprolactinemia treatment, to assess the effect of the estrogen deficiency on bone.

Men

  • In men, the most common symptoms of Prolactinoma are impotence and diminished libido.
  • Pressure of the tumor on surrounding tissues may lead to headaches or eye problems caused by the enlarged pituitary pressing against nearby eye nerves. 
  • Patients with macroadenomas may also have hypopituitarism because of pressure of the tumor on the normal gland.  Therefore, it is important to measure the other pituitary hormones as well.

What other conditions cause prolactin levels to rise?

In some people, high blood levels of prolactin can be traced to causes other than a pituitary tumor.

What Tests are Done in Patients with a Prolactinoma?

A doctor will test for prolactin blood levels in women with unexplained milk secretion (galactorrhea), or irregular or absent menses or infertility, and in men with impaired sexual function. Thyroid function tests will be drawn and a history obtained to include other conditions and medications known to raise prolactin secretion. In a woman with amenorrhea, a routine pregnancy test should be performed, as prolactin levels are routinely elevated in pregnancy. Then, an MRI scan will be performed to detect the presence of a pituitary tumor and determining the size. The MRI scan will also be used to look for effects of the tumor on surrounding tissues.  Other tests include assessment of production of other pituitary hormones, to insure they are normal. Depending on the size of the tumor, an eye exam with measurement of visual fields (to detect loss of peripheral vision) may be performed.

Treatment

Medical treatment

The goal of treatment is to return prolactin secretion to normal, reduce tumor size, correct any visual abnormalities and restore normal pituitary function. In the case of very large tumors, only partial achievement of this goal may be possible. Because dopamine is the chemical that normally inhibits prolactin secretion, doctors first treat a prolactinoma with dopamine agents (agonists).

Bromocriptine shrinks the tumor and returns prolactin levels to normal in the majority of patients. To avoid side effects such as nausea and dizziness, it is important for bromocriptine treatment to start slowly. Usual maintenance doses are 2.5 (one tablet) to 7.5 mg (3 tablets) daily.

Bromocriptine treatment should not be interrupted without consulting an endocrinologist. Prolactin levels often rise again in most people when the drug is discontinued.

Another dopamine agonist is cabergoline, which may be more effective and better tolerated than bromocriptine. Another advantage of cabergoline is that it may be prescribed as a weekly dosage of 0.5 (one tablet) to 2.0 (4 tablets) mg weekly.

Surgery

Surgery should be considered if medical therapy cannot be tolerated or if it is ineffective in reducing prolactin levels or tumor size. The results of surgery depend a great deal on tumor size and prolactin level as well as the skill and experience of the neurosurgeon. It may still be necessary to prescribe dopamine agonists after surgery if the tumor has been incompletely removed.

Radiation Therapy

Radiation therapy should be considered if either medical therapy or surgery is ineffective in reducing prolactin levels or tumor size. The type of radiation therapy used will depend on the size and location of the tumor.

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