What Is It?
The pituitary gland is a pea-sized structure that is attached to the undersurface of the brain by a thin stalk. It is protected by a cradle of bone called the sella turcica, which is located above the nasal passages, almost directly behind the eyes. The pituitary gland sometimes is called the master gland because it produces such a large number of hormones, including those that regulate body growth, adrenal gland function and the production of breast milk.
When tumors develop within the pituitary gland, they are usually small, well-localized, slow-growing masses that arise from one specific family of hormone-producing pituitary cells. Although these tumors almost always are benign (noncancerous), they have the potential to cause significant systemic (whole-body) symptoms if they produce excessive amounts of pituitary hormones. They also can grow large enough to press on the nearby optic nerves (nerves that carry vision impulses from the eyes to the brain) or on parts of the brain itself.
A pituitary tumor is classified as belonging to one of four main types, based on whether it overproduces pituitary hormones, and the specific type of hormone produced:
- ACTH-producing tumor — This pituitary tumor, which also is called a basophilic adrenocorticotrophic hormone-secreting adenoma, overproduces adrenocorticotrophic hormone (ACTH). ACTH is the pituitary hormone that regulates hormone production by the adrenal gland. When this type of pituitary tumor releases excess amounts of ACTH into the bloodstream, the excess ACTH overstimulates the adrenal glands to pour out high levels of adrenal glucocorticoids (adrenal hormones) and androgens (male hormones) into the blood. In most cases, an ACTH-producing tumor is small and doesn’t enlarge beyond the sella turcica.
- Prolactin-producing tumor — This pituitary tumor, which also is called a prolactin-secreting adenoma, overproduces the hormone prolactin, which stimulates the breasts to make milk. Prolactin-producing pituitary tumors can develop in both men and women, and they sometimes grow so big that they press on the sella turcica and cause it to enlarge. This enlargement of the sella turcica can be seen on skull X-rays or diagnostic scans, and often is an important clue that a pituitary tumor exists.
- Growth hormone-producing tumor — This tumor, which also is called an eosinophilic growth hormone-secreting adenoma, secretes abnormally large amounts of growth hormone. This overproduction of growth hormone causes giantism (excessive growth, especially in height) in children and teen-agers and acromegaly (abnormal enlargement of the skull, jaw, hands and feet, and other symptoms of abnormal growth) in adults. Growth hormone-producing tumors can enlarge beyond the sella turcica.
- Non-functioning pituitary tumor — This type of pituitary tumor, which also is called a hormonally inactive adenoma, does not produce pituitary hormones, and is slow to produce symptoms. For this reason, this type of tumor tends to grow large before it is discovered. In many cases, a nonfunctioning pituitary adenoma is diagnosed only when it already has enlarged beyond the sella turcica and has begun to cause problems related to pressure on the optic nerves or brain.
In the United States, pituitary tumors are diagnosed in one to 15 of every 200,000 people each year, most commonly in women between the ages of 15 and 44. However, autopsy studies suggest that a much larger percentage of the population — perhaps as high as 11 percent — may have very tiny pituitary tumors that never cause symptoms.
A pituitary tumor causes symptoms that are related to the type of hormone it produces:
- ACTH-producing tumor — This tumor produces symptoms of Cushing’s disease, a condition caused by prolonged overproduction of adrenal glucocorticoids and androgens. Symptoms of Cushing’s disease include: obesity that is most noticeable on the trunk of the body; thin skin; easy bruising; red or purple lines (striae) on the skin of the abdomen; a moon-shaped face; muscle wasting; excess body hair in women; acne; absence of menstrual periods (amenorrhea); and psychiatric symptoms, especially depression. Cushing’s disease also can trigger osteoporosis, high blood pressure (hypertension) and diabetes.
- Prolactin-producing tumor — In women, this tumor occasionally causes a woman who is not pregnant or nursing to produce breast milk, a condition called galactorrhea. Much more often, it causes absent periods (amenorrhea). In men, it causes impotence, decreased sex drive, thinning of the beard and decreased body hair. If the tumor enlarges beyond the sella turcica, it also can cause one or more of the following: a general decrease in vision, a loss of vision in only one or two visual fields, eye-muscle paralysis and headache.
- Growth hormone-producing tumor — If this tumor develops before puberty, then the child typically has the following symptoms of giantism (also called gigantism): abnormally rapid growth, unusually tall stature, a very large head, coarse facial features, very large hands and feet, and, sometimes, behavioral and visual problems. If the tumor develops after puberty, then the adult patient has the following symptoms of acromegaly: thick, oily skin, coarse features with thick lips and a broad nose, prominent cheekbones, a protruding forehead and lower jaw, a deep voice, enlargement of the hands and feet, a barrel-shaped chest, excessive sweating, and pain and stiffness in the joints.
- Nonfunctioning pituitary tumor — These tumors usually are diagnosed because they have enlarged beyond the sella turcica and are causing pressure on the optic nerves and brain. The most common symptoms include a general decrease in vision, a loss of vision in only one or two visual fields, eye-muscle paralysis and headache. These tumors can cause partial or complete deficiency of pituitary hormones.
Your doctor will review your symptoms, medical history and current medications. This information is very important because certain medical conditions and/or prescription drugs can have significant effects on your levels of body hormones. For example, psychiatric drugs called neuroleptics can increase blood levels of prolactin, and prescription glucocorticoids (even therapeutic injections of dexamethasone (Decadron and other brand names) into injured joints) can cause high blood levels of glucocorticoids. Also, medical conditions such as hypothyroidism and kidney failure can cause unusually high blood levels of prolactin.
During a physical examination, your doctor will look for the characteristic signs that signal overproduction of a particular pituitary hormone. For example, your doctor may look for breast-milk production caused by a prolactin-producing tumor, or a moon-shaped face and abdominal marks caused by an ACTH-producing tumor.
Depending on the results of your physical examination, your doctor will order one or more of the following tests:
- Sophisticated blood tests to measure hormone levels
- X-rays, tomograms or a Computed tomography (CT) scan of the skull
- A magnetic resonance imaging (MRI) scan of the head combined with an injection of gadolinium, a dye used to highlight brain structures
- A thorough eye examination by an ophthalmologist, including perimetry studies (eye tests that detect vision loss in specific visual fields)
In most cases, a pituitary tumor will continue to grow until it is treated. Sometimes, however, a prolactin-secreting tumor will stabilize, or even improve, without treatment.
Since doctors do not know why pituitary tumors develop, there is no way to prevent them.
Doctors have two main goals in treating pituitary tumors: to reduce the abnormally high levels of hormones, and to shrink the tumor to prevent pressure damage to the optic nerves and brain. These goals are accomplished in slightly different ways, depending on the specific type of pituitary tumor:
- ACTH-producing tumor — Most people with this type of pituitary tumor undergo a surgical procedure called transsphenoidal hypophysectomy. In this procedure, the surgeon removes the pituitary tumor through an incision in the upper portion of the nasal passages. After surgery, levels of glucocorticoid hormones are abnormally low, so the patient typically needs to take supplemental glucocorticoid medication for about three to 12 months. This medication gradually is tapered as the body slowly reestablishes a normal working relationship between the pituitary gland and the adrenal glands. If surgery is not effective, then radiation therapy will be needed.
- Prolactin-producing tumor — The preferred treatment for this type of tumor is medical therapy with drugs called long-acting dopamine agonists, such as bromocriptine (Parlodel), pergolide (Permax) or cabergoline (Dostinex). These drugs not only reduce blood levels of prolactin, but also shrink the size of the pituitary tumor in about 75 percent of cases. If medical therapy is ineffective, the tumor can be removed surgically with a transsphenoidal hypophysectomy.
- Growth hormone-producing tumor — Transsphenoidal hypophysectomy is usually the first choice, followed by medical therapy with either a somatostatin analog (some form of the drug octreotide, sold as Sandostatin), bromocriptine, or one of the long-acting dopamine analogs (pergolide or cabergoline). Radiation therapy is used in people who do not respond to surgery or medication.
- Nonfunctioning pituitary tumor — Many doctors do not treat small, nonfunctioning pituitary tumors, if the tumor is less than 10 millimeters in size. Instead, they monitor the growth of the tumor with periodic MRI scans. Larger tumors are removed surgically using a transsphenoidal hypophysectomy, followed by radiation therapy to eliminate any remaining tumor.
Transsphenoidal hypophysectomy is a safe and effective procedure that is popular for cosmetic reasons. However, not all pituitary tumors can be removed by using this surgical approach, either because the tumor is too large or in a position that is difficult to reach through the nose. Instead, the surgeon must perform a procedure called a craniotomy, which removes the tumor through an incision in the front portion of the skull.
When To Call A Professional
Make an appointment to see your doctor if:
- You have frequent headaches.
- You notice that your vision is becoming less sharp.
- You have trouble seeing objects in a particular visual field.
- You think that you might have symptoms of Cushing’s disease or acromegaly.
- You are a woman who has unexplained absent periods or is producing breast milk when you are not nursing.
- You are a man who is impotent or has decreased sexual desire.
- You are a parent who is worried that your child is growing faster or taller than expected.
The prognosis depends on the type of pituitary tumor:
- ACTH-producing tumor — After surgery, the cure rate is 80 percent to 90 percent for ACTH-producing tumors that have not enlarged beyond the sella turcica. When surgery fails and radiation therapy is used, 83 percent of treated patients go into remission (symptoms disappear).
- Prolactin-producing tumor — Medical treatment is safe and effective in almost all cases, even when the tumor is fairly large. In women of childbearing age whose periods disappear because of a prolactin-producing pituitary tumor, medical treatment usually restores fertility.
- Growth hormone-producing tumor — Approximately 90 percent of tumors measuring less than 1 centimeter in diameter (microadenomas), and approximately 50 percent of tumors measuring more than 1 centimeter in diameter (macroadenomas), can be cured with surgery. In patients treated medically, octreotide relieves symptoms in most cases, especially headaches (95 percent of patients).
- Non-functioning pituitary tumor — Because this type of tumor tends to be large when it is diagnosed, a transsphenoidal hypophysectomy often cannot remove the entire tumor mass. Even so, surgery usually can improve vision, if pressure from the tumor had been causing eye problems.
Diseases and Conditions Center
All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.