Neurosurgical Diseases and Disorders (M-Z) / Prolactinoma

Prolactinoma

General Information

• The UCLA Pituitary Tumor Program offers comprehensive management of prolactinomas
• This type of pituitary tumor (adenoma) produces an excessive amount of the hormone prolactin.
• Prolactinomas are the most common type of hormonally-active pituitary tumor.

What is Prolactin?

• Prolactin is a hormone produced by the pituitary gland that is makes breastfeeding of newborns possible.
• At the end of pregnancy, the pituitary gland begins producing more prolactin. This important hormone causes several body changes:
  • Breast milk is produced (doctors call this "galactorrhea")
  • Menstrual periods are stopped ("amenorrhea")
  • Sexual interest (libido) is decreased
• Once breastfeeding is stopped (or never begun), prolactin levels drop back to normal and normal menstrual periods begin again
• The brain controls the amount of prolactin production using a natural chemical ("neuropeptide") called dopamine. The more dopamine is sent down to the pituitary gland, the less prolactin that is made.

Prolactin is a hormone essential for milk production by the breast. The release of prolactin is controlled by the amount of dopamine produced by the brain

Symptoms

• In women:
  • Relatively small increases in prolactin cause irregular menstrual periods or complete loss of menses. For this reason, most prolactinomas are discovered when they are small in size.
  • In many cases (more common with higher prolactin levels), there is milk production by the breasts
  • Some women complain of a reduced sex drive
  • Large prolactinomas are uncommonly found in women. If the tumor is large enough, it may cause hypopituitarism, visual loss, and headache (see Symptoms In Men below)
• In men:
  • Symptoms are usually caused as a result of the size of the tumor rather than the hormonal effects of prolactin
    • In some cases, men experience enlargement of the breast tissue ("gynecomastia")
  • Large pituitary tumors ("macroadenomas") may cause:
    • Some degree of pituitary failure (hypopituitarism) due to compression of the normal pituitary gland. The most common symptom is loss of sex drive (low libido).
    • Visual loss from compression of the optic nerves. This is typically loss of peripheral vision first.
    • Headache
• A minority of patients with large tumors may have acute bleeding into the tumor (pituitary apoplexy), causing the sudden onset of headache, visual loss, double vision, and/or pituitary failure. Immediate medical attention is usually required

Diagnosis

• Hormonal
  • A blood test, measuring the level of prolactin, usually establishes the diagnosis.
  • Not all cases of elevated prolactin are due to prolactinomas. Other possible causes include:
    • Pregnancy
    • Stress
    • Low thyroid function
    • Kidney failure
    • Liver failure
    • A large pituitary tumor (or other tumor occuring in the same area) that causes compression of the pituitary stalk (the connection between the brain and the pituitary gland). Compression of the pituitary stalk interferes with dopamine from the brain reaching the pituitary gland. Because dopamine normally inhibits prolactin release, the normal pituitary gland produces more prolactin (prolactin levels are usually less than 200)
  • The blood prolactin level is usually proportional to the size of the tumor.
    • Large tumors may have prolactin levels in the thousands
    • In some cases, very high prolactin levels can overwhelm the blood test, resulting is a falsely measured prolactin level (typically reported as only slightly above normal). If a prolactinoma is suspected based on clinical symptoms, it is important to have the test repeated using a diluted sample of blood (the so-called "Hook Effect")
• MRI Imaging
  •  Most prolactinomas can be detected using magnetic resonance imaging (MRI) of the pituitary gland
    • It is best to obtain a special MRI "Pituitary Protocol" in order to best visualize the tumor
  •  Smaller tumors may not be visible using computed tomography (CT) scans

MRI image of the side-view of the head (midway through the brain) showing a prolactinoma. On the right is the same image that has been colorized, showing that the top part of the tumor (shown in red) elevates the optic nerve (actually, the optic chiasm)

Treatment

• Medical therapy
  • In general, the first line of treatment for patients with a prolactinoma is medical rather than surgical.
  • Most patients (80 percent) will have their prolactin levels restored to normal with medication alone.
  • The medications mimick the activity of dopamine, thereby sending the message to the prolactin-producing cells to stop making prolactin.
    • Cabergoline (Dostinex) is usually the preferred medication because it is very effective, has the fewest side effects, and the easiest dosing schedule (twice a week). It is more expensive, however
    • Bromocriptine (Parlodel) is sometimes used, but its effectiveness is commonly limited by side effects (most common are nausea, headache, and dizziness)
  • With treatment, most women experience a return of menses and many become fertile again. The size of the prolactinoma will be reduced in the majority of patients, which can improve vision and end headaches.
  • The management of medical therapy for fertility and during pregnancy requires special consideration. As of now, Cabergoline is not FDA-approved for use during pregnancy, and therefore bromocriptine may be necessary
• Surgery
  • For patients that do not respond to medical treatment with cabergoline or bromocriptine, surgery is considered
    • Ideally, surgery should be performed within six months of starting medical treatment because the tumor may become more difficult to remove thereafter. Transsphenoidal surgery is effective for women with relatively small adenomas.
  • The long-term cure rate is 80 percent to 90 percent. The cure rate is lower for larger tumors, particularly in men.
  • Urgent transphenoidal surgery is advised for patients with pituitary apoplexy.
• Radiotherapy
  • Because most patients with prolactinomas respond well to medical therapy, radiation is used in few patients.
  • Stereotactic radiation is generally preferred over external beam radiation therapy because a higher dose of radiation can be delivered to the tumor and less to normal brain structures.

The Neuro-ICU cares for patients with all types of neurosurgical and neurological injuries, including stroke, brain hemorrhage, trauma and tumors. We work in close cooperation with your surgeon or medical doctor with whom you have had initial contact. Together with the surgeon or medical doctor, the Neuro-ICU attending physician and team members direct your family member's care while in the ICU. The Neuro-ICU team consists of the bedside nurses, nurse practitioners, physicians in specialty training (Fellows) and attending physicians. UCLA Neuro ICU Family Guide