In vertebrate anatomy, the pituitary gland, or hypophysis, is an endocrine gland about the size of a pea and weighing 0.5 grams (0.018 oz) in humans.Encyclopedia Entry for Pituitary :Pituitary apoplexy. The pituitary is a small gland at the base of the brain. The pituitary produces many of the hormones that control essential body processes. Pituitary apoplexy can be caused by bleeding into the pituitary or by blocked blood flow to the pituitary. Apoplexy means bleeding into an organ or loss of blood flow to an organ. Pituitary apoplexy is commonly caused by bleeding inside a noncancerous ( benign ) tumor of the pituitary. These tumors are very common. The pituitary is damaged when the tumor suddenly enlarges and either bleeds into the pituitary or blocks blood supply to the pituitary. The larger the tumor, the higher the risk for pituitary apoplexy. When pituitary bleeding occurs in a woman during or right after childbirth, it is called Sheehan syndrome. This is a very rare condition. Risk factors for pituitary apoplexy in non-pregnant people without a tumor include: Bleeding disorders Diabetes Head injury Radiation to the pituitary gland Use of a breathing machine Pituitary apoplexy in these situations is very rare.Pituitary apoplexy usually has a short period of symptoms (acute), which can be life threatening. Symptoms often include: Severe headache (worst of your life) Paralysis of the eye muscles, causing double vision ( ophthalmoplegia ) or problems opening an eyelid Loss of peripheral vision or loss of all vision in one or both eyes Low blood pressure, nausea, loss of appetite, and vomiting from acute adrenal insufficiency Personality changes due to sudden narrowing of one of the arteries in the brain (anterior cerebral artery) Less commonly, pituitary dysfunction may appear more slowly. In Sheehan syndrome, for example, the first symptom may be a failure to produce milk caused by a lack of the hormone prolactin. Over time, problems with other pituitary hormones may develop, causing symptoms of the following conditions: Growth hormone deficiency Adrenal insufficiency (if not already present or treated) Hypogonadism (body's sex glands produce little or no hormones) Hypothyroidism (thyroid gland does not make enough thyroid hormone) In rare cases, when the posterior (back part) of the pituitary is involved, symptoms may include: Failure of the uterus to contract to give birth to a baby (in women) Failure to produce breast milk (in women) Frequent urination and severe thirst (diabetes insipidus).The health care provider will perform a physical exam and ask about your symptoms. Tests that may be ordered include: Eye exams MRI or CT scan Blood tests will be done to check levels of: ACTH (adrenocorticotropic hormone) Cortisol FSH (follicle-stimulating hormone) Growth hormone LH (luteinizing hormone) Prolactin TSH (thyroid-stimulating hormone) Insulin-like growth factor-1 (IGF-1) Sodium Osmolarity in blood and urine.Acute apoplexy may require surgery to relieve pressure on the pituitary and improve vision symptoms. Severe cases need emergency surgery. If vision is not affected, surgery is often not necessary. Immediate treatment with adrenal replacement hormones (glucocorticoids) may be needed. These hormones are often given through the vein (by IV). Other hormones may eventually be replaced, including: Growth hormone Sex hormones (estrogen/testosterone) Thyroid hormone Vasopressin (ADH).Acute pituitary apoplexy can be life threatening. The outlook is good for people who have long-term (chronic) pituitary deficiency that is diagnosed and treated.Complications of untreated pituitary apoplexy can include: Adrenal crisis (condition that occurs when there is not enough cortisol, a hormone produced by the adrenal glands ) Vision loss If other missing hormones are not replaced, symptoms of hypothyroidism and hypogonadism may develop.Call your provider if you have any symptoms of chronic pituitary insufficiency. Go to the emergency room or call the local emergency number (such as 911) if you have symptoms of acute pituitary apoplexy, including: Eye weakness or vision loss Sudden, severe headache Low blood pressure (which can cause fainting) Nausea Vomiting If you develop these symptoms and you have already been diagnosed with a pituitary tumor, seek medical help right away.Pituitary infarction; Pituitary tumor apoplexy.Endocrine glands Endocrine glands.Melmed S, Kleinberg D. Pituitary masses and tumors.Encyclopedia Entry for Pituitary :Pituitary tumor. Most pituitary tumors are noncancerous ( benign ). Up to 20% of people have pituitary tumors. Many of these tumors do not cause symptoms and are never diagnosed during the person's lifetime. The pituitary is part of the endocrine system. The pituitary helps control the release of hormones from other endocrine glands, such as the thyroid, sex glands (testes or ovaries), and adrenal glands. The pituitary also releases hormones that directly affect body tissues, such as bones and the breast milk glands. The pituitary hormones include: Adrenocorticotropic hormone (ACTH) Growth hormone (GH) Prolactin Thyroid-stimulating hormone (TSH) Luteinizing hormone (LH) and follicle-stimulating hormone (FSH) Pituitary gland Watch this video about: Pituitary gland As a pituitary tumor grows, the normal hormone-releasing cells of the pituitary may be damaged. This results in the pituitary gland not producing enough of its hormones. This condition is called hypopituitarism. The causes of pituitary tumors are unknown. Some tumors are part of a hereditary disorder called multiple endocrine neoplasia I (MEN I). The pituitary gland can be affected by brain tumors that develop in the same part of the brain, resulting in similar symptoms.Some pituitary tumors produce too much of one or more hormones. As a result, symptoms of one or more of the following conditions can occur: Hyperthyroidism (thyroid gland makes too much of its hormones; this is an extremely rare condition of pituitary tumors) Cushing syndrome (body has a higher than normal level of the hormone cortisol) Gigantism (abnormal growth due to higher than normal level of growth hormone during childhood) or acromegaly (higher than normal level of growth hormone in adults) Nipple discharge and irregular or absent menstrual periods in women Decreased sexual function in men Symptoms caused by pressure from a larger pituitary tumor may include: Changes in vision such as double vision, visual field loss (loss of peripheral vision), drooping eyelids or changes in color vision Headache Lack of energy Nasal drainage of clear fluid Nausea and vomiting Problems with the sense of smell In rare cases, these symptoms occur suddenly and can be severe ( pituitary apoplexy ).Your health care provider will perform a physical examination. The provider will note any problems with double vision and visual field, such as a loss of side (peripheral) vision or the ability to see in certain areas. The exam will check for signs of too much cortisol (Cushing syndrome) or too much growth hormone (acromegaly). Tests to check endocrine function may be ordered, including: Cortisol levels: dexamethasone suppression test , urine cortisol test FSH level Insulin growth factor-1 (IGF-1) level LH level Prolactin level Testosterone/estradiol levels Thyroid hormone levels: free T4 test , TSH test Tests that help confirm the diagnosis include the following: Visual fields MRI of head.Surgery to remove the tumor is often needed, especially if the tumor is pressing on the nerves that control vision (optic nerves). Most of the time, pituitary tumors can be surgically removed through the nose and sinuses. If the tumor cannot be removed this way, it is removed through the skull. Radiation therapy may be used to shrink the tumor in people who cannot have surgery. It may also be used if the tumor returns after surgery. In some cases, medicines are prescribed to shrink certain types of tumors.These resources can provide more information on pituitary tumors: National Cancer Institute -- www.cancer.gov/types/pituitary Pituitary Network Association -- pituitary.org The Pituitary Society -- www.pituitarysociety.org.If the tumor can be surgically removed, the outlook is fair to good, depending on whether the entire tumor is removed.The most serious complication is blindness. This can occur if the optic nerve is seriously damaged. The tumor or its removal may cause lifelong hormone imbalances. The affected hormones may need to be replaced, and you may need to take medicine for the rest of your life. Tumors and surgery can sometimes damage the posterior pituitary (back part of the gland). This can lead to diabetes insipidus , a condition with symptoms of frequent urination and extreme thirst.Call your provider if you develop any symptoms of a pituitary tumor.Tumor - pituitary; Pituitary adenoma.Endocrine glands Endocrine glands The pituitary gland Pituitary gland.Dorsey JF, Hollander AB, Alonso-Basanta M, et al. Cancer of the central nervous system.