Prolactinoma

Overview

What is prolactinoma?

A prolactinoma is a benign (non-cancerous) tumor that forms in your pituitary gland and causes excess production of prolactin, a hormone.

At least half of all prolactinomas are very small (less than 1 centimeter or 3/8 of an inch in diameter). These small tumors are called microprolactinomas and happen more often in people assigned female at birth (AFAB).

Larger prolactinomas are more common in people assigned male at birth (AMAB), and they tend to occur at an older age. Tumors larger than 3/8 of an inch or 1 centimeter in diameter are called macroprolactinomas.

What is prolactin?

Prolactin (also known as lactotropin) is a hormone that’s mainly responsible for the development of mammary glands within breast tissue, milk production and lactation. It also contributes to several bodily processes and functions. Your pituitary gland is mainly responsible for producing and secreting prolactin, but your central nervous system, immune system, uterus and mammary glands are also capable of producing prolactin.

Prolactin levels are normally low in people assigned male at birth (AMAB) and non-lactating and non-pregnant people. They’re normally elevated in people who are pregnant or breastfeeding (chestfeeding).

Having higher-than-normal levels of prolactin in your blood (hyperprolactinemia) — usually caused by a prolactinoma — can cause infertility and other issues.

What is the pituitary gland?

Your pituitary gland is a small, grape-sized gland located at the base of your brain below your hypothalamus. It’s a part of your endocrine system and is in charge of making many different important hormones. Your pituitary gland also tells other endocrine system glands to release hormones.

Who gets prolactinomas?

Prolactinomas occur most commonly in people under the age of 40. They’re more common in people assigned female at birth than people assigned male at birth and rarely occur in children and adolescents.

How common are prolactinomas?

Small, non-cancerous pituitary tumors (adenomas) are fairly common in the general population. Approximately 40% of pituitary tumor cases are prolactinomas, making it the most common type of pituitary tumor.

Symptoms and Causes

What are the symptoms of a prolactinoma?

The symptoms of a prolactinoma can vary depending on how much excess prolactin it’s producing and its size and location.

For people assigned female at birth (AFAB), common symptoms of having a prolactinoma include:

For people assigned male at birth (AMAB), common symptoms of a prolactinoma include:

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

People assigned female at birth (AFAB) often report symptoms earlier due to noticing changes in their periods or milky discharge from their nipples when they’re not pregnant or breastfeeding. However, people AFAB who are taking sex hormones — via birth control pills or hormone therapy — may not experience these symptoms.

People who have reached menopause and people assigned male at birth often have a delayed diagnosis due to a lack of clear signs and symptoms.

Can a prolactinoma cause weight gain?

A prolactinoma may lead to weight gain in certain cases when it’s associated with other pituitary hormone issues like hypothyroidism or increased cortisol production, which can cause weight gain.

What causes prolactinomas?

The cause of prolactinomas is unknown. In some cases, genetic factors may play a role. For instance, having an inherited condition called multiple endocrine neoplasia (MEN) type 1 increases your risk for prolactinomas.

Diagnosis and Tests

How is a prolactinoma diagnosed?

Prolactinomas are often detected at an earlier stage in people assigned female at birth (AFAB) due to irregular periods.

If you’re experiencing symptoms of prolactinomas, your healthcare provider will likely recommend testing, such as blood tests and imaging tests, to confirm or rule out a prolactinoma diagnosis.

Which tests are used to diagnose a prolactinoma?

If your healthcare provider suspects that you may have a prolactinoma, they’ll recommend that you undergo one or more of the following tests:

  • Prolactin level blood test: If your blood test results reveal that you have higher-than-normal prolactin levels in your blood, your provider will likely have you undergo image testing to confirm or rule out a prolactinoma diagnosis.
  • MRI (magnetic resonance imaging) scan: The preferred imaging test to diagnose a prolactinoma is the MRI scan. This procedure uses radio waves and magnets to create detailed images of your internal organs and soft tissues. An MRI scan can help your provider locate a prolactinoma and determine its size.
  • CT (computed tomography) scan: If you have a pacemaker or other metal implant in your body, you’ll likely not be able to get an MRI. In this case, your provider may recommend a CT scan instead. A CT uses a series of X-ray images taken at different angles and a computer to create images of tissues inside your body. The results of the CT scan will likely allow your provider to confirm a diagnosis of prolactinoma and determine its size and location.
  • Testosterone level blood test: If you’re a person assigned male at birth (AMB) and are experiencing prolactinoma symptoms, your provider will likely want to test the level of testosterone in your blood. Low levels of testosterone can help confirm a prolactinoma diagnosis.

If your provider has diagnosed you with prolactinoma, they may recommend having you undergo additional blood tests to check the levels of other pituitary hormones, which can be affected by a prolactinoma. If you have a large prolactinoma, your provider may recommend a vision test to see if it could be affecting your vision.

Management and Treatment

How is a prolactinoma treated?

Healthcare providers usually treat prolactinomas with medications. In rare cases, healthcare providers use surgery or radiation therapy.

The goals of treatment for prolactinomas include:

  • Bringing your prolactin levels back to normal.
  • Shrinking the tumor.
  • Making sure your pituitary gland is working properly.
  • Correcting any problems caused by the tumor, such as irregular periods, low testosterone levels, headaches or vision issues.

What medications and treatments are used to treat prolactinomas?

Treatment options for prolactinomas include:

  • Medication (most common).
  • Surgery.
  • Radiation therapy.

Medications for prolactinomas

Medications called dopamine agonists control your prolactin levels and are very effective in shrinking prolactinoma tumors.

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

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

You will likely have to take either of these medications for at least two years to prevent the prolactinoma from growing back, especially if the tumor is large. After two years, your healthcare provider may slowly reduce your dosage and eventually stop the medication if your prolactin levels are normal and the tumor is no longer visible. If your prolactin levels rise again, you may need to go back on the medication for as long as it takes to bring your prolactin levels to an optimum range.

Surgery for prolactinomas

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

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

Surgeons use two types of surgeries to remove prolactinomas, including:

  • Transsphenoidal surgery: This is the most common surgery to treat prolactinomas. A surgeon performs the surgery through an incision (small cut) at the back of your nasal cavity or under your upper lip.
  • Transcranial surgery: Surgeons usually only use this type of surgery if the tumor is large or has spread to other areas. A surgeon removes the tumor through an opening in your skull.

As with all surgeries, there are possible complications and risks associated with prolactinoma surgery, including:

  • Infection.
  • Impaired pituitary function (hypopituitarism).
  • Temporary diabetes insipidus which is a rare condition that leads to frequent urination and excessive thirst. This is not to be confused with diabetes mellitus (Type 1 or Type 2 diabetes).
  • Cerebrospinal fluid leak.

Radiation therapy

Radiation therapy is a rare third option for treating prolactinomas if medications and/or surgery don’t work to reduce your prolactin levels.

Radiation therapy uses high-energy X-rays or particle waves to kill tumor cells. Depending on the size and location of the tumor, you may receive one radiation dose or multiple doses over several weeks.

Side effects and complications of radiation therapy for prolactinoma treatment include:

  • Low levels of thyroid hormone (most common side effect).
  • A decrease in levels of other pituitary gland hormones.
  • Vision loss (rare side effect).
  • Brain injury (rare side effect).

Prevention

What are the risk factors for developing a prolactinoma?

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

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

Outlook / Prognosis

What is the outlook (prognosis) for prolactinoma?

The prognosis (outlook) for prolactinomas is generally good. Medication (dopamine agonists) shrinks small prolactinoma tumors and brings prolactin levels back to normal for four out of five people receiving 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 prolactinomas and in 50% of people who have large tumors. For people with larger prolactinomas that can only be partially removed, medications can often return their prolactin levels to a normal range after surgery.

Although prolactinomas are not life-threatening, they can cause certain issues such as infertility and vision changes. Because of this, it’s important to receive treatment if you have a prolactinoma.

Living With

When should I see my healthcare provider?

If you’re experiencing symptoms of a prolactinoma, such as milky discharge from your nipples without being pregnant or breastfeeding (chestfeeding), contact your healthcare provider.

If you’re taking medication for your prolactinomas and are experiencing concerning symptoms, contact your provider.

People who take medication to treat their prolactinomas are usually on the medication for a long time — usually at least two years. If you’re taking medication, you’ll likely need to see your provider regularly to monitor the tumor and your prolactin levels.

Frequently Asked Questions

Does a prolactinoma require surgery?

In most cases, prolactinomas can be treated with just medication. If medication does not work, you may need to have surgery to remove the tumor.

Does prolactinoma go away?

A prolactinoma won’t go away on its own without treatment. Long-term medication can shrink the tumor until it’s gone. However, it’s important to note that prolactinomas can come back, even after successful treatment with medication or surgery.

A note from Cleveland Clinic

Finding out you have a tumor can be scary. The good news is that prolactinomas are benign (non-cancerous) and highly treatable. If you have any questions about prolactinoma or your treatment plan, don’t be afraid to ask your healthcare provider. They’re there to help you.

Last reviewed by a Cleveland Clinic medical professional on 01/05/2022.

References

  • MedlinePlus. Prolactinoma. (https://medlineplus.gov/ency/article/000336.htm) Accessed 1/5/2022.
  • National Institute of Diabetes and Digestive and Kidney Diseases. Prolactinoma. (https://www.niddk.nih.gov/health-information/endocrine-diseases/prolactinoma) Accessed 1/5/2022.

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