A prolactinoma is a type of pituitary gland tumor that requires care from pituitary specialists. At the OHSU Pituitary Center, you will find:

• A team of pituitary experts who work will together to care for you.
• The expertise to give you a precise diagnosis and a care plan tailored to your needs.
• A high-volume center that treats more than 1,500 patients with pituitary conditions a year.
• Skilled neurosurgeons who use minimally invasive techniques for an easier recovery.
• Close follow-up care for large prolactinomas, based on our own research.
• Access to clinical trials testing the latest approaches to treatment.

Learn more about:

• Understanding pituitary disorders
• Diagnosis and treatment of pituitary disorders at OHSU

What is a prolactinoma?

Prolactinomas are the most common type of pituitary adenoma — a noncancerous tumor on the pea-size pituitary gland. A prolactinoma causes the body to make too much prolactin, a hormone.

Prolactin is important for making breast milk. It can also play a role in your energy production (metabolism), fertility and sexual desire. Men and women produce prolactin.

Scientists don’t know what causes these tumors to form. If the tumor is small, treatment with medication is usually successful. Larger tumors are less predictable and may require more aggressive treatment, such as surgery.

Who gets prolactinomas?

Age and sex: Men and women at any age can develop a prolactinoma, but women ages 20 to 34 are at highest risk. Prolactinomas are rare in children.

Prevalence: About one to three people in 10,000 have a prolactinoma that causes symptoms.

“Silent” prolactinomas: About 5-10% of adults have a prolactinoma that causes no symptoms. Many people don’t know they have one, and doctors rarely treat them if discovered.

Symptoms and complications of prolactinomas

Some symptoms are related to high levels of prolactin. Others, such as vision problems, are linked to a tumor pressing on an optic nerve.

Women may have:

• Production of breast milk when not pregnant or nursing
• Menstrual changes, such as irregular periods or no periods
• Infertility
• Reduced sex drive
• Headaches
• Vision problems

Men may have:

• Headaches
• Vision problems
• Impotence
• Infertility
• Decreased interest in sex

Untreated, a prolactinoma can cause:

• Reduced hormone production if the tumor presses on the pituitary gland, which may lead to symptoms such as weight loss or fatigue
• Osteoporosis (brittle, fragile bones)
• Pregnancy complications

Types of prolactinomas

Doctors may classify a prolactinoma by its size:

Microprolactinomas: These are small tumors that generally respond to treatment.

Macroprolactinomas: These are larger tumors that also generally respond to treatment but that may require more aggressive therapy.

Diagnosing prolactinomas

Diagnosing prolactinomas can be challenging. Prolactin levels can be high for reasons other than a tumor, requiring expert evaluation.

At the OHSU Pituitary Center, we do specialized blood tests to ensure an accurate reading. We also offer the expertise to zero in on your pituitary condition and avoid a misdiagnosis.

Tests for prolactinomas

Exam: We will start with a physical exam and discussion of your medical history.

Blood tests: These can help us see if your pituitary gland is making too much prolactin. We can also detect other pituitary hormonal changes.

• A normal prolactin level is less than 20 nanograms per milliliter.
• A prolactin level of more than 150-200 nanograms per milliliter usually signals a prolactinoma.

Confirming a diagnosis

Many other conditions can slightly increase prolactin levels, including:

• Pregnancy
• Stress
• Low thyroid function
• Other pituitary tumors, such as a craniopharyngioma
• Certain antidepressants and anti-nausea medications

We need to rule these out to confirm a diagnosis. We may recommend:

• Pregnancy test: This can rule out pregnancy for women of childbearing age.
• An MRI scan helps us determine the size and location of any growth on the pituitary gland.
• A neuro-ophthalmology exam may help if you are having vision problems.

Prolactinoma treatments

Medication returns prolactin levels to normal for about 80% of patients with a prolactinoma. Some patients benefit from surgery.

Medication

Medications such as bromocriptine and cabergoline, taken as pills, can lower prolactin levels and shrink the tumor. We may use MRI or CT scans to make sure the tumor is shrinking.

Many patients take medication indefinitely, though some eventually stop under a doctor’s guidance.

Surgery

If you need surgery, it’s important to see a highly experienced neurosurgeon such as the ones at OHSU. Removing a prolactinoma is complex. Our surgeons do more than 100 tumor surgeries in and around the pituitary gland each year. This high level of experience improves the chances of success. 

You may need surgery to remove a prolactinoma if:

• It does not get smaller after taking medication.
• It grows.
• You have a large tumor and plan for pregnancy soon.
• You still have symptoms after trying medication.
• Side effects such as nausea and dizziness prevent you from taking medication.

What to expect from surgery:

• Minimally invasive procedure: We use transsphenoidal surgery to remove the tumor through the nose. This precise surgery leaves little or no visible scarring, and usually comes with a more comfortable recovery.
• Excellent results: In top medical centers such as OHSU, surgery can lead to a cure in 80% of patients with small tumors. The rate is lower for patients with large tumors that surgeons can’t completely remove. Even then, a combination of surgery and medication can lower prolactin levels to normal, reducing or eliminating symptoms and restoring fertility.

Follow-up care

Prolactinomas can come back within five years. We will monitor you, especially if you had a large prolactinoma. Our research shows that these tumors can be especially aggressive in men.

We have also developed ways to predict how likely a tumor is to return, based on a study of more than 800 of our surgical patients.

Prolactinoma treatment during pregnancy

If you are pregnant and have a prolactinoma, your doctor will monitor you carefully to see if the tumor grows. You will need regular vision tests, because prolactinomas often develop close to an optic nerve connecting an eye to the brain.

We encourage women who have a prolactinoma and wish to get pregnant to talk with their doctor. Women with small prolactinomas can get pregnant and expect a healthy pregnancy. For women who have large tumors, we may recommend that you have surgery before becoming pregnant.

We usually recommend that women stop taking medications during pregnancy. After giving birth, talk with your doctor about treatment options.

Clinical trials

We are a national leader in offering clinical trials to test promising new approaches. Your care team will talk with you about any trial that is right for you.

Learn more

• Prolactinoma, National Institute of Diabetes and Digestive and Kidney Diseases
• Prolactinomas, Pituitary Network Association