They are usually noncancerous but can cause a wide variety of symptoms

By Jennifer Welsh 

 Medically reviewed by Doru Paul, MD

A pituitary tumor is an abnormal growth of cells in the pituitary gland.¹ These growths are almost always benign, but some can be cancer. The most common pituitary tumor is the pituitary adenoma.²

Sometimes these tumors are found by accident and cause no symptoms, but other times they cause changes in vision or unusual symptoms from changes in hormones. About 10,000 people are diagnosed with pituitary tumors every year in the United States.³

The pituitary gland is an essential hormone-secreting gland. It's a small piece of tissue located at the base of the brain. Therefore, pituitary tumors are a type of brain tumor.

The pituitary gland is part of the body's endocrine system, which produces hormones. The pituitary gland releases hormones that control many needed bodily functions. These hormones play a role in reproduction, childhood growth, metabolism, stress response, and thyroid function.

This article will provide an overview of pituitary tumors of all types, including their symptoms, causes, diagnosis, treatment, and prognosis. 

Moyo Studio / Getty Images

Types of Pituitary Tumor

Pituitary tumors can be cancerous (malignant) or noncancerous (benign). Most pituitary tumors are noncancerous.

The most common pituitary tumor is the pituitary adenoma. Pituitary adenomas are divided into two types, as follows:⁴

• Benign pituitary adenomas are noncancerous, grow very slowly, and do not spread. These are also called pituitary neuroendocrine tumors.²

• Invasive pituitary adenomas are cancer. They grow and spread to other parts of the brain.

Pituitary adenomas are classified by size, such as:

• Microadenomas are smaller than 1 centimeter. 

• Macroadenomas are bigger than 1 centimeter. 

Pituitary tumors are divided into two types based on their effect on the body. Functional tumors produce hormones that impact other body functions. Nonfunctional tumors do not change the body's hormone levels.⁴ Functioning tumors cause varying effects based on which hormone levels they change.²

Functional pituitary adenomas often have special names based on their impact on hormone levels and the unusual symptoms that sometimes follow.

For example, a prolactinoma, or lactotroph adenoma, is a pituitary adenoma that causes the gland to release too much prolactin, leading to irregular menstrual periods and erectile dysfunction. Prolactinoma is the most common hormone-producing pituitary tumor.

Other functional adenomas include:⁵

• Somatotroph adenomas make growth hormones.

• Corticotroph adenomas activate the body's stress hormones.

• Thyrotroph adenomas activate the thyroid.

• Gonadotroph adenomas make reproductive hormones.

Another type of pituitary tumor is pituitary carcinoma, a very rare type of cancer. It can grow quickly and spread to other brain and body parts.⁴ It has often already spread by the time it is discovered.⁶

Symptoms

Because the pituitary gland controls many of the body's hormones, functional tumors that disrupt these hormones can cause many symptoms.⁷

Generally, pituitary tumors can cause problems that include:

• Vision changes, including loss of visual field, blurred or double vision, color blindness, and loss of peripheral vision

• A severe headache called pituitary tumor apoplexy that comes on suddenly at the front of the head or behind one or both eyes

• Dizziness, loss of consciousness

• Nausea, vomiting

• Weakness, fatigue

• Decreased sexual function and libido (sex drive)

• Mood changes

A drop in hormone levels due to a pituitary tumor, called hypopituitarism, can cause:⁸

• Diabetes insipidus, a rare disorder in which the body can't regulate fluids properly

• Stunted growth, or dwarfism, which results in short stature

• Addison's disease, a dysregulation of the stress hormone cortisol

• An underactive thyroid, called hypothyroidism, makes too little hormone

• Insufficient production of sex hormones, called hypogonadism

On the other hand, increases in pituitary hormones from a tumor, called hyperpituitarism, can cause:⁹

• Acromegaly, an overproduction of growth hormone that leads to enlarged features of gigantism.

• Cushing's syndrome, a rare disorder in which the body makes too much stress hormone cortisol

• Unusual production of breast milk called galactorrhea

• Hyperthyroidism, when the thyroid gland produces too much hormone

Causes

Some pituitary tumors result from genetic diseases called multiple endocrine neoplasias (MEN). This group of hereditary illnesses causes tumors on the hormone-producing organs, including the pituitary gland. These tumors may be cancerous, but they are also often benign.⁴

Other genetic diseases that may cause a pituitary tumor include:¹⁰

• McCune-Albright syndrome

• Carney complex 

• Isolated familial acromegaly

Most of the time, though, the cause of pituitary tumors is unknown. 

Diagnosis

Healthcare providers diagnose pituitary tumors using various tests:¹¹

• A physical examination

• A complete medical history

• Blood and urine tests to check for hormone levels and other components

• Imaging tests, like magnetic resonance imaging (MRI)

• Computerized visual field test to measure the extent of vision loss

• A genetic test if a multiple endocrine neoplasia is suspected

• Biopsy (taking a small tumor sample to examine in the lab and check for cancer)

Treatment

Many noncancerous tumors may not need treatment. They may have been discovered incidentally while testing for another condition, or they may be very slow-growing and not cause symptoms.⁴

If hormone changes due to the tumor are causing symptoms, medications such as the following can help many avoid surgery:⁵

• Prolactinomas are treated with drugs that mimic the brain chemical dopamine. For 80% to 90% of people, these drugs shrink the pituitary tumor and lower prolactin levels.¹²

• Tumors causing acromegaly might benefit from hormone-mimicking drugs, but surgery is often warranted in these cases.¹³

When medications are no longer helping, or the tumor is causing significant visual symptoms, the treatment for pituitary tumors is surgery.

Nonfunctional pituitary tumors may benefit from external radiation therapy to kill cancer cells instead of surgery. Medications like chemotherapy may also help shrink the tumor, especially when surgery isn’t an option.

Prognosis

The prognosis of a pituitary tumor depends on what type of tumor it is, if it’s cancerous or not, and if it’s functional. 

Most pituitary tumors are not severe. They often are silent, do not cause symptoms, and are discovered through testing for another disorder. Many people can live for a long time with a pituitary tumor.²

While pituitary tumors are rarely diagnosed, they may be more common than thought. Imaging tests on people who have died from other causes indicate that about 25% of people have pituitary adenomas without knowing it.³

A pituitary tumor can be life-threatening if it is:

• Cancerous

• Inoperable (can’t be operated on or removed)

• Spreads to other parts of the brain or body 

• Is functional and creates hormone imbalances that can’t be fixed with medication 

Coping

A diagnosis of a pituitary tumor can be very upsetting. It is normal to have ongoing concerns about the tumor, even if it is not producing symptoms or you have been successfully treated for it.¹⁴ Work with your treatment team to get answers to any questions about your prognosis, treatment options, and side effects and challenges you may face.

Ask your family and friends for emotional and physical support after diagnosis and during treatment. You may benefit from a support group of people who have faced a pituitary tumor or similar health challenge. A mental health professional or counselor may also be able to help you through this difficult time.

Summary

Pituitary tumors are clumps of cells that grow in a part of the brain called the pituitary gland. This gland controls vital actions in the body. 

Pituitary tumors may be cancerous and spread to the brain and body. But most often, they are benign. Pituitary adenomas are the most common type of pituitary tumor. Pituitary carcinoma is the name for cancer in the pituitary gland. This is very rare.

A pituitary tumor can cause vision changes, headaches, and other signs of hormonal changes. Sometimes, people need to take drugs to control the symptoms of a pituitary tumor. If pituitary tumors grow too large, they may need surgery. 

14 Sources

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American Cancer Society. Treatment of functional (hormone-making) pituitary tumors.

American Cancer Society. Treatment of pituitary carcinomas.

American Cancer Society. Signs & symptoms of pituitary tumors.

Kim SY. Diagnosis and treatment of hypopituitarism. Endocrinol Metab. 2015;30(4):443-455. doi:10.3803/EnM.2015.30.4.443

Wang AR, Gill JR. The pituitary gland: an infrequent but multifaceted contributor to death. Acad Forensic Pathol. 2016;6(2):206-216. doi:10.23907/2016.023

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American Cancer Society. Life after pituitary tumor treatment.

By Jennifer Welsh
Jennifer Welsh is a Connecticut-based science writer and editor with over ten years of experience under her belt. She’s previously worked and written for WIRED Science, The Scientist, Discover Magazine, LiveScience, and Business Insider.