Prolactinoma

What is prolactinoma?

Prolactinoma is a generally benign (noncancerous) tumor that forms in your pituitary gland and makes more prolactin — a hormone — than you need. About 50% of pituitary tumor (pituitary adenoma) cases are prolactinomas, making them the most common type of pituitary tumor.

Prolactin is mainly responsible for the development of mammary glands within breast tissue and lactation. It contributes to several other bodily processes as well. Prolactinomas cause higher-than-normal levels of prolactin in your blood (hyperprolactinemia), resulting in infertility and other issues.

The thought of having a tumor so close to your brain can be unsettling. You may breathe a little easier knowing that prolactinomas aren’t life-threatening. But they can cause unwanted health issues, so it’s important to seek care if you develop symptoms.

Types of prolactinomas

There are two main types of prolactinomas based on their size:

• Microprolactinomas: These tumors are very small — less than 1 centimeter or 3/8 of an inch in diameter. They represent at least half of prolactinoma cases and more commonly affect women and people assigned female at birth (AFAB).
• Macroprolactinomas: These tumors are larger than 3/8 of an inch or 1 centimeter in diameter. They’re more common in men and people assigned male at birth (AMAB) and tend to occur at an older age.

Among people with prolactinomas, as many as 60% of people AMAB have macroprolactinomas, while 90% of people AFAB have microprolactinomas.

What are the symptoms of prolactinoma?

The symptoms of prolactinoma can vary depending on how much prolactin it produces and its size.

Symptoms of prolactinoma in adults include:

• Changes in menstruation that aren’t related to menopause, like irregular periods or no periods (amenorrhea).
• Milky nipple discharge when not pregnant or breastfeeding (galactorrhea).
• Vaginal dryness, which can make penetrative sex painful.
• Male infertility or female infertility.
• Low libido (sex drive).
• Weight gain.
• Erectile dysfunction (ED).
• Enlarged breast tissue (gynecomastia) in people assigned male at birth (AMAB).

Left untreated, high prolactin levels can also lead to osteopenia and/or osteoporosis.

If the prolactinoma is large (macroprolactinoma), it may also cause the following symptoms:

• Headaches.
• Nausea and/or vomiting.
• Vision changes, like double vision or decreased peripheral vision.
• Sinus pain or pressure.
• Problems with your sense of smell (dysosmia).

People assigned female at birth (AFAB) often notice symptoms earlier due to changes in their periods or milky nipple discharge. But people AFAB who’re taking hormonal medications — like birth control pills or hormone replacement therapy — may not experience these symptoms.

People who have reached menopause and people AMAB often have a delayed diagnosis.

Prolactinoma symptoms in children

It’s very rare for children to develop a prolactinoma. But if they do, prolactinomas typically cause delayed puberty.

What causes prolactinomas?

Researchers don’t know the exact cause of prolactinoma. Many cases happen randomly (sporadically). But certain genetic conditions can increase your risk for prolactinoma, including:

• Multiple endocrine neoplasia (MEN) type 1.
• MEN type 4.
• Familial isolated pituitary adenomas (FIPA).

How is prolactinoma diagnosed?

Your healthcare provider will ask about your symptoms and medical history and do a physical exam. If you have milky nipple discharge, they may do a breast exam. They’ll likely recommend one or more of the following tests to diagnose prolactinoma:

• Prolactin blood test: If your blood test result reveals that you have higher-than-normal prolactin levels, your provider will likely recommend image testing to confirm or rule out a prolactinoma diagnosis.
• MRI scan or CT scan: These imaging tests can help your provider locate the tumor and determine its size. Providers prefer using MRI scans to diagnose prolactinomas, but a CT scan is the next option if an MRI scan isn’t safe for you.
• Testosterone level blood test: If you’re a person AMAB, your provider will likely want to test your testosterone levels.

If you receive a prolactinoma diagnosis, your provider may recommend additional blood tests to check the levels of other pituitary hormones. If you have a large prolactinoma, your provider may recommend an eye exam to see if it’s affecting your vision.

What is the treatment for prolactinoma?

Prolactinomas are often highly treatable. Healthcare providers usually prescribe medication to treat them. In rare cases, your provider may recommend surgery or radiation therapy.

Prolactinoma medication

Medications called dopamine agonists are often very effective in shrinking prolactinoma tumors. They can also return your prolactin level to a healthy range.

The two dopamine agonists that healthcare providers prescribe to treat prolactinomas are cabergoline and bromocriptine. Cabergoline is often the first-choice medication because it’s more effective than bromocriptine and has fewer side effects.

Common side effects of dopamine agonists include nausea, vomiting and dizziness.

You’ll likely have to take either of these medications for at least two years to prevent the tumor from growing back, especially if it’s large. After two years, your provider may slowly reduce your dosage and then stop the medication if your prolactin levels are normal and the tumor is no longer visible.

Surgery for prolactinomas

Although it’s rare, you may need to have surgery to treat prolactinoma for any of the following reasons:

• You’re having negative reactions to dopamine agonists.
• The dopamine agonists aren’t working to shrink the tumor.
• You take antipsychotic medications that interact with dopamine agonists.
• You have a large prolactinoma and want to surgically remove it before trying to become pregnant.

Together, you and your healthcare provider will decide if surgery is the best option for you. Surgeons use two types of surgeries to remove prolactinomas, including:

• Transsphenoidal surgery: This is the most common surgery for prolactinomas. A surgeon makes an incision (small cut) at the back of your nasal cavity or under your upper lip to access your pituitary gland and the tumor.
• Transcranial surgery: For this surgery, a surgeon removes the tumor through an opening in your skull. They typically only use this type of surgery if the tumor is very large.

As with all surgeries, there are possible complications and risks associated with prolactinoma surgery. Your provider will go over these risks with you.

Radiation therapy for prolactinomas

Radiation therapy is a rare third option for treating prolactinomas if medications and/or surgery don’t work to reduce your prolactin levels. Depending on the size and location of the tumor, you may receive one radiation dose or multiple doses over several weeks.

Is prolactinoma preventable?

Unfortunately, there’s nothing you can do to prevent developing prolactinoma. A known risk factor is having an inherited (passed through your biological family) condition called multiple endocrine neoplasia (MEN) type 1.

If you have a first-degree relative (biological sibling or parent) who has this condition, you may want to get genetic counseling to check if you have it as well. This may help screen for and catch prolactinoma in its early phases.

What is the prognosis for someone with prolactinoma?

The prognosis (outlook) for someone with prolactinoma is generally good. Medication (dopamine agonists) shrinks small prolactinoma tumors and brings prolactin levels back to normal for 4 out of 5 people receiving this treatment.

Prolactinoma surgery is also often successful. When an experienced surgeon performs the surgery, it corrects prolactin levels in about 90% of people with small tumors and in 50% of those who have large tumors. If you have a large tumor that can only be partially removed, medications can often return your prolactin levels to a normal range after surgery.

When should I see my healthcare provider?

If you’re taking medication to treat prolactinoma, you’ll likely be on it for a long time — typically, at least two years. If you’re taking medication, you’ll likely need to see your healthcare provider regularly to monitor the tumor and your prolactin levels.

If you experience concerning symptoms after starting medication, contact your provider.