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Hypopituitarism

Definition

Hypopituitarism is a condition caused by low levels of pituitary hormones.

Causes, incidence, and risk factors

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.

Symptoms

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

Signs and tests

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

Treatment

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.

Expectations (prognosis)

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

Complications

Side effects of drug therapy can develop.

Calling your health care provider

Call your health care provider if symptoms of hypopituitarism develop.

Prevention

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