The pituitary gland is a small structure that is located just below the brain. It is attached by a stalk to the hypothalamus, the area of the brain that controls its function.

The hormones secreted by the pituitary and their functions are:

• growth hormone (GH), which stimulates growth of tissues and bone
• thyroid stimulating hormone (TSH), which stimulates the thyroid gland to secrete hormones that affect body metabolism
• adrenocorticotropic hormone (ACTH), which stimulates the adrenal gland to secrete cortisol which helps to maintain blood pressure
• prolactin, which stimulates female breast development and milk production
• luteinizing hormone (LH), which controls sexual function in males and females
• follicle stimulating hormone (FSH), which controls sexual function in males and females
• antidiuretic hormone (ADH), which controls water loss by the kidneys
• oxytocin, which stimulates contraction of the uterus during labor and milk release from the breasts.

In hypopituitarism, there is an absence of one or more pituitary hormones. Lack of the hormone leads to loss of function in the gland or organ that it controls. (For example, loss of thyroid stimulating hormone leads to loss of function in the thyroid gland.)

Hypopituitarism may be caused by tumors of the pituitary gland or hypothalamus, head trauma, brain tumor, radiation, brain surgery, stroke, or infections of the brain and the tissues that support the brain. Occasionally, hypopituitarism is due to uncommon immune system or metabolic diseases such as sarcoidosis, histiocytosis X, and hemochromatosis.

Hypopituitarism is also a rare complication following pregnancy, a condition called Sheehan's syndrome. The cause of hypopituitarism is unknown.

• fatigue
• weakness
• sensitivity to cold
• decreased appetite
• weight loss
• abdominal pain
• low blood pressure
• headache
• visual disturbances
• short stature (less than 5 feet) if onset is during a growth period
• loss of armpit or pubic hair
• in women: cessation of menstrual periods, infertility, or failure to lactate
• in men: decreased sexual interest, loss of body or facial hair
• in children: slowed growth and sexual development

Note: Symptoms may develop slowly and may vary greatly depending upon the severity of the disorder and the number of deficient hormones and their target organs.

Additional symptoms that may be associated with this disease:

• weight gain (unintentional)
• joint stiffness
• hoarseness or changing voice
• hair loss
• facial swelling

Diagnosis of hypopituitarism must confirm decreased hormone levels due to an abnormality of the pituitary gland and rule out disease of the target organ.

• cranial CT scan, revealing a tumor or abnormal mass in the pituitary gland
• cranial MRI, revealing a tumor or abnormal mass in the pituitary or hypothalamus
• serum luteinizing hormone (LH), decreased or normal
• serum follicle stimulating hormone (FSH), decreased or normal
• serum testosterone level, decreased
• serum estradiol (estrogen), decreased
• serum cortisol, decreased
• serum ACTH, decreased
• T4 (thyroid hormone), decreased
• serum thyroid stimulating hormone (TSH), decreased or normal
• serum thyroid stimulating hormone response to thyroid-releasing hormone, decreased
• serum growth hormone (GH), decreased
• serum insulin-like growth factor 1 (IGF-1), decreased

If hypopituitarism is caused by a tumor, treatment by surgical removal and/or radiation therapy may be indicated. However, replacement of deficient hormones is often required even after successful treatment of a pituitary tumor.

Hormone therapy is needed to replace hormones no longer made by organs under the control of the pituitary gland. These include corticosteroids (cortisol), thyroid hormone, sex hormones (testosterone for men and estrogen for women), and growth hormone. Drugs are also available to treat associated infertility in men and women.

Hypopituitarism is usually permanent and requires life-long treatment; however, a normal life span can be expected.

Side effects of drug therapy can develop.

Call your health care provider if symptoms of hypopituitarism develop.

In most cases, the disorder is not preventable. Awareness of risk may allow early diagnosis and treatment.