Keywords
Acromegaly «» Cushing's Syndrome «» Prolactinomas

What are pituitary tumors?
What are the symptoms of pituitary tumors?
How are pituitary tumors diagnosed?
How are pituitary tumors treated?

What are pituitary tumors?

Pituitary tumors (also known as pituitary adenomas) result from abnormal growth of cells within the pituitary gland which is located at the base of the skull, in a cavity known as the sella tursica. This gland is the "master gland" of the body and is connected to the overlying brain by the pituitary stalk, though which the brain regulates the production, release, and storage of several important hormones. The hormones released by the pituitary gland travel through the blood to various other glands and tissues in the body and control their function. The main hormones produced by the pituitary gland include Adrenocorticotorpic Hormone (ACTH - triggers the adrenal glands to release cortisol, which regulates metabolism and blood pressure), Thyroid Stimulating Hormone (TSH - causes the thyroid gland to release thyroid hormones which control the basal metabolic rate and play an important role in growth and maturation), Growth Hormone (GH - regulates growth and metabolism), Luteinizing Hormone and Follicle Stimulating Hormone (LH and FSH - control the production of sex hormones, estrogen and testosterone), Melanocyte-Stimulating Hormone (MSH - regulates the production of melanin in the skin which is a pigment that protects against harmful rays from the sun), and Prolactin (stimulates production of breast milk).

As pituitary tumors enlarge, the pressure or damage from the mass can lead to dysfunction of the pituitary gland which is manifested, among other symptoms, by deficiencies of its hormone(s). This is typically seen in non-hormone producing tumors of the pituitary gland. On the other hand, if the tumor itself produces any of the hormones normally made by the gland, then an exaggeration of the effects of the hormone within the body can also be seen.

What are the symptoms of pituitary tumors?

Pituitary tumors can cause a variety of symptoms depending on their size and whether or not they produce any hormones. Tumors which secrete hormones (functioning tumors) are usually small and do not generally cause neurological symptoms or dysfunction of the entire pituitary gland (also known as hypopituitarism). Instead, the symptoms relate to the specific hormone that is produced by the tumor. The three most common functioning pituitary tumors produce prolactin, growth hormone, or ACTH.

Prolactinomas are prolactin-secreting tumors which are among the most common types of pituitary tumors. Symptoms are usually the result of decrease in the sex hormones, estrogen in women and testosterone in men. Therefore, presentation differs between the sexes with women usually experiencing amenorrhea (lack of menses), galactorrhea (abnormal breast milk production), infertility, and symptoms of estrogen deficiency (osteoporosis, vaginal dryness, hot flashes, and irritability). Males usually present with loss of libido and impotence due to suppressed male hormone levels.

Acromegaly is caused by an overproduction of growth hormone which can cause swelling of the hands and feet, brow and lower jaw protrusion, arthritis, increase in spacing between teeth, enlarged tongue, heart and kidney failure, loss of vision due to pressure on optic nerves from tissue overgrowth, headaches, diabetes mellitus, and high blood pressure.

Cushing's Syndrome is the result of an overproduction of ACTH and it can lead to elevated cortisol levels. This elevation in cortisol, in turn, leads to rapid weight gain (particularly of the trunk and face with sparing of the limbs), excess sweating, thinning of the skin (which causes easy bruising) purple or red striations of the skin, muscle weakness in the hips and shoulders, abnormal male-pattern hair growth, insomnia, reduced libido, impotence, amenorrhea (lack of menses in women), infertility, psychological disturbances, anxiety, persistent high blood pressure, high blood sugars, heart disease, and increased pigmentation of the skin.

For non-hormone producing tumors, symptoms generally are due to growth in size of the tumor which leads to dysfunction of the gland or pressure on surrounding neurologic structures. The symptoms may include lack of energy, weight loss, nausea, vomiting, constipation, irregular or absent menses, infertility, dry or increased pigmentation of the skin, cold intolerance, mental status changes (such as sleepiness or psychosis), and headaches. Also, pressure on nearby nerves can cause double vision, facial numbness, or progressive visual loss which begins with loss of peripheral vision and can progress to blindness.

How are pituitary tumors diagnosed?

Magnetic resonance imaging (MRI) is the most sensitive diagnostic method for tumors of the pituitary gland, allowing visualization of the location and size of the tumor. This technique, however, is not accurate in determining the specific type of pituitary tumor that may be present. Therefore, evaluation of pituitary function is also an important diagnostic tool which can then determine the best treatment option. The function of the pituitary gland is generally evaluated through a simple measurement of various hormone levels in the blood and/or urine. Other types of tests may also be necessary to judge pituitary function -- examples include measuring the level of growth hormone after ingestion of a sugar solution or measurement of blood ACTH and cortisol levels after taking a steroid medication by mouth. Formal evaluation of visual fields can also be useful in tracking visual changes through the course of treatment.

How are pituitary tumors treated?

Depending on the size, type, and the symptoms caused by the pituitary tumor, medical or surgical therapy may be indicated. Medical therapy is useful in treating some hormone secreting adenomas, such as prolactinomas, ACTH-secreting tumors, and GH-secreting tumors.

Prolactinomas can be treated with medications that are called dopamine agonists, such as bromocriptine or carbergoline. In about 85% of cases, patients will normalize their prolactin levels, and almost 80% of tumors will decrease in size in response to dopamine agonists.

ACTH-secreting tumors, which cause Cushing's disease, are more difficult to treat than prolactinomas due to their side effects and poor response rates. Two classes of medication are generally used which either interfere with the production of steroids in the adrenal glands or act within the brain to decrease the amount of corticosteroids. When all medical therapy and pituitary surgery fail to treat the symptoms, removal of the adrenal glands may be an option; however, this may lead to rapid growth of the pituitary tumor and massive blood levels of ACTH. In turn, ACTH stimulates melanin production in the skin, darkening the skin color, in a condition called Nelson's syndrome.

GH-secreting tumors lead to acromegaly and there are three types of medications which can be used to treat this condition: dopamine agonists, somatostatin analogs, and peripheral GH blockers. Most patients treated with dopamine agonists, such as bromocriptine, achieve reduction in their GH levels, but usually not down to normal levels. Somatostatin analogs are medications that are injected once every few weeks to achieve low levels of growth hormone; however, as with dopamine agonists, very few decrease their GH to levels which are considered a cure. Peripheral GH blockers are the third generation of medical treatment for acromegaly which can normalize GH levels in more than 90% of patients.

If medical therapy fails or for tumors that are large enough to compress local brain structures and cause significant neurologic symptoms, pituitary surgery may be an option. Most of these surgeries are done through what is called a transsphenoidal approach, which avoids many of the complications of traditional open brain surgery, in addition to being safe, effective, and requiring a shorter hospital stay. While surgery has the advantage of rapidly lowering hormone levels, risks of the procedure generally do not outweigh the benefits for patients who are appropriate candidates for medical therapy. Therefore, a collaborative approach (involving an endocrinologist and an neurosurgeon) is essential in assuring proper treatment.

Radiation therapy may also be an option in cases when medical therapy and surgery have failed or are not an option. This mode of therapy uses high-energy x-rays to destroy abnormal pituitary cells and shrink tumors. There are various types of radiation therapy which include Standard External Beam Radiotherapy (nonselective radiation that damages all cells in the path of the beam), Proton Beam Treatment (radiation that can direct a specific beam to the region of the the tumor, thereby causing less damage to normal tissues surrounding the tumor), and Gamma Knife Irradiation (which combines standard external beam radiotherapy with a technique that focuses the radiation to the tumor in order to cause less damage to tissues adjacent to the pituitary gland).