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Pituitary Adenoma

Most pituitary adenomas are slow growing and benign, which means they do not spread to other parts of the body. However, as they grow, they can put pressure on nearby structures, such as the nerves that connect the eyes to the brain, and cause symptoms.


What is the pituitary?

The pituitary is a pea-sized gland that connects to the base of the brain. It is located behind the nose and sphenoid sinus (air cavity at the back of the face), just below another important and related structure called the hypothalamus.

This gland is an organ that makes and releases special substances, acting on other organs and tissues, such as hormones. The pituitary gland is called the "master gland" because its hormones regulate the balance of hormones produced by most of the other glands in the body. In this way, the pituitary controls many processes such as growth, development, and reproduction. It also checks the function of certain organs such as the kidneys, breasts, and uterus.

The pituitary has three sections or lobes, each with its own function in the body. The anterior lobe, the anterior pituitary, makes up about 80% of the gland and is located closest to the front of the head. Its job is to make and release many "signaling" hormones into the bloodstream. These hormones move through the blood to other glands and organs, where they signal the organs and glands to start or stop working.

The intermediate lobe secretes only one hormone. This hormone affects skin pigmentation.

The posterior pituitary, the posterior part of the gland, does not make hormones on its own. Instead, it contains the nerve endings of brain cells from the hypothalamus. These brain cells produce hormones that are stored in the posterior pituitary for later use.

The hypothalamus and pituitary work hand in hand. The hypothalamus produces hormones that signal the pituitary to release its hormones.

What is a pituitary adenoma?

A pituitary adenoma is a growth or tumor in the pituitary. Most pituitary adenomas are slow growing and benign, which means they are not cancerous and do not spread to other parts of the body. However, as they grow, they can put pressure on nearby structures, such as the nerves that connect the eyes to the brain, and cause symptoms. This is known as the “mass effect”.

A large adenoma can also crush normal pituitary cells and prevent them from working properly, leading to a condition called hypopituitarism. This can cause low blood pressure, fatigue, and changes in your sex drive and function. It can also make you feel less inept at managing stress.

Pituitary adenomas are labeled according to their size. Tumors smaller than 1 cm are called microadenomas. Tumors larger than 1 cm are called macroadenomas. Many adenomas cause symptoms by releasing extra hormones into the bloodstream, but not all adenomas produce hormones.

Some, called non-functioning or empty cell adenomas, do not produce hormones. About one-third of all pituitary tumors are dysfunctional adenomas. They are often found because they enlarge and cause symptoms due to the mass effect.

How common are pituitary adenomas?

Pituitary adenomas account for 10% to 15% of all tumors that develop inside the skull. Although believed to occur in as many as 20% of people at some point in their lives, they are present in about 77 out of 100,000 people. However, many pituitary adenomas, especially microadenomas, do not cause serious symptoms and are never found. Macroadenomas are about twice as common as microadenomas. Pituitary adenomas can occur at any age, but are more common in people in their 30s or 40s. They are rarely found in those under the age of 20. Women have adenomas more often than men.


What causes pituitary adenomas?

The exact cause of pituitary adenomas is unknown. However, some are linked to random changes in the DNA that make up our genes inside a cell. (Genes are instructions for making proteins that control a cell's function.) These changes cause cells in the pituitary to become abnormal and grow out of control, forming a tumor. Changes can be passed from parents to their children (inherited), but usually happen on their own during a person's lifetime.

What are the symptoms of pituitary adenoma?

Symptoms of pituitary adenomas vary depending on the type of hormone secreted by the tumor or the mass effect on nearby structures. Having too many hormones can lead to certain disorders or syndromes, including:

  • Giantness in children and acromegaly in adults due to too much growth hormone (GH)

  • Cushing's disease, which is caused by too much adrenocorticotropic hormone (ACTH), triggers the adrenal glands to produce steroid hormones.

  • Hyperthyroidism caused by too much thyroid stimulating hormone (TSH)

Some common symptoms of pituitary adenomas include:

  • headache

  • Vision problems (double vision, vision loss)

  • nausea or vomiting

  • Behavior changes, including aggression, depression, and anxiety

  • changes in sense of smell

  • nasal drainage

  • sexual dysfunction

  • Infertility

  • Fatigue (extreme tiredness)

  • Unexplained weight gain or loss

  • Painful joints or muscle weakness

  • early menopause

  • Changes in your monthly period (women)


How are pituitary adenomas diagnosed?

If your doctor thinks you may have a pituitary adenoma, he or she will do a complete review of your symptoms and medical history and perform a physical exam. Laboratory tests may be done to check the hormone levels in your blood. An imaging test such as an MRI or CT scan* can show the enlargement of the pituitary. These tests can confirm the diagnosis of pituitary adenoma. If you have vision problems, the doctor may also want you to have a visual field test to check your eye function. Sometimes, pituitary adenomas are found incidentally when doing an MRI or CT for another condition.

MRI uses a large magnet, radio waves, and a computer to create clear images of the body. CT uses computers to combine many X-ray images into cross-sectional views of the inside of the body.


How are pituitary adenomas treated?

Pituitary adenomas are usually treated with surgery, medication, radiation, or a combination of these treatments.

Surgery: Doctors can usually remove the tumor with endoscopic surgery, accessing the pituitary gland using very small instruments and a camera inserted into a small opening made through the nose and sinuses. This approach is called the transsphenoidal technique. In cases where this approach cannot be used, the physician must open the skull to access the pituitary and adenoma.

Medical treatment: In some types of pituitary adenomas, the tumor can be treated with drugs that shrink the tumor and relieve symptoms.

Radiation: Radiation therapy uses high-energy X-rays to kill cancer cells and shrink tumors. A special form of radiation therapy called stereotactic radiosurgery uses high-dose radiation that precisely targets the adenoma from multiple directions to prevent the tumor from growing.

In some cases, the doctor may choose to use annual tests to check that the adenoma is not growing while monitoring the patient for any symptoms. This can happen with small tumors that do not cause serious symptoms, and in people with other significant medical conditions.


Can pituitary adenomas be prevented?

Pituitary adenomas cannot be prevented.


What is the prognosis for people with pituitary adenomas?

The outlook depends on the size and type of adenoma you have. When treatment destroys the tumor, most patients with benign adenomas can return to their full and normal lives. Adenomas can recur, which means you will need repeat treatment. About 18% of patients with prolactinomas, the most common type of hormone-releasing adenomas, and about 18% of patients with non-functioning adenomas will need further treatment at some point. In some cases, adenoma treatment causes low hormone levels and you need to take hormone pills to replace what you lost.

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