Hypopituitarism Health Article

Definition

Hypopituitarism, also known as the underactivity of the pituitary gland (an endocrine gland), is loss of function in the pituitary and the failure to secrete hormones that affect many of the body's functions. The pea-sized pituitary gland is located at the base of the brain, and is attached (by a stalk) to the hypothalamus. Patients diagnosed with hypopituitarism may be deficient in one or several hormones or have complete pituitary failure.

Description

The pituitary gland regulates many hormones that control various functions and organs within the body. Some of these regulatory substances and target glands that can be affected by hypopituitarism are those of the reproductive system, growth hormones, as well as the thyroid and pituitary glands. Hypopituitarism can affect both males and females of any age.

In hypopituitarism, interference with the production and release of some hormones affects the function of the target gland. Commonly affected hormones may include:

Reproductive hormones (i.e., gonadotropin deficiency)

Gonadotropin deficiency involves two distinct hormones affecting the reproductive system. Luteinizing hormone (LH) stimulates the testes in men and the ovaries in women. This deficiency can affect both male and female fertility, and menstruation. Follicle-stimulating hormone (FSH) has similar effects to LH.

Thyroid-stimulating hormone

Thyroid-stimulating hormone (TSH) is involved in stimulation of the thyroid gland. A lack of stimulation (deficiency) in the gland leads to hypothyroidism.

Adrenocorticotopic hormone

Also known as corticotropin, adrenocorticotopic hormone (ACTH) stimulates the adrenal gland to produce a hormone similar to cortisone, called cortisol. The loss of this hormone (deficiency) can lead to serious problems.

Growth hormone

Growth hormone (GH) regulates the body's growth. Patients who lose supply of this hormone before physical maturity will suffer impaired growth. Loss of the hormone can also affect adults.

Other hormone deficiencies

If a test calculates normal levels of prolactin, deficiency of the hormone is eliminated as a diagnosis. A thyrotropin-releasing hormone (TRH) simulation test can determine prolactin levels. A number of tests are available to detect ADH levels.

Multiple hormone deficiencies

Patients with multiple hormone deficiencies will show symptoms of one or more specific hormone deficiencies or some of the generalized symptoms listed above.

Panhypopituitarism

The insulin-induced hypoglycemia, or ITT that is used to determine specific hormone deficiencies, is an excellent test to diagnose panhypopituitarism. This test can reveal levels of growth hormone, ACTH (cortisol) and prolactin deficiency. The presence of insufficient levels of all of these hormones is a good indicator of complete pituitary failure. Imaging studies and clinical history are also important.

Causes and symptoms

There are several factors that can lead to the damage of the pituitary gland and the development of hypopituitarism. Causes can be congenital (from birth) or developed at a later stage in life. Interference in the interaction between the pituitary gland and the hypothalamus or other endocrine gland—such as tumors, inflammation, infection, lesions, or interruption of blood supply—can lead to an underactive pituitary gland. Interruption of the delivery of hormones may include certain tumors and aneurysms. Damage to the gland, from severe head injury, radiographic therapy (i.e., for cancers such as leukemia), or surgery can also lead to hypopituitarism.

Another cause of hypopituitarism can be damage to the pituitary gland cells. Destroyed cells cannot produce the pituitary hormones that would normally be secreted by the gland. Cells may be destroyed by a number of diseases and tumors.

Symptoms of hypopituitarism vary with the affected hormones and severity of hormone deficiency. Frequently, patients can have years of nonspecific symptoms that present when major illness or increased levels of stress occur. Overall symptoms may include fatigue, sensitivity to cold, weakness, decreased appetite, weight loss, and abdominal pain. Low blood pressure (hypotension), headache, and visual disturbances are other associated symptoms.

Symptoms specific to individual hormone deficiencies are as follows:

Gonadotropin deficiency

Replacement of gonadal steroids is common treatment for LH and FSH deficiency. Estrogen for women and testosterone for men will be prescribed in the lowest effective dosing regimens possible, since there can be complications to this therapy. To correct women's loss of libido, small doses of androgens may be prescribed. To restore fertility in men, regular hormone injections may be required. Male and female patients whose hypopituitarism results from hypothalamic disease may be successfully treated with a hypothalamic-releasing hormone (GnRH), which can restore gonadal function and fertility.

Thyroid stimulating hormone deficiency

In patients who have hypothyroidism, the function of the adrenal glands will be tested and treated with steroids before thyroid hormone replacement is administered.

Adrenocorticotopic hormone deficiency

Hydrocortisone, or cortisone, may be given to compensate for this hormone deficiency. Most patients require 20 mg or less of hydrocortisone per day.

Growth hormone deficiency

It is essential to treat children suffering from growth hormone deficiency. The effectiveness of growth hormone therapy in adults, particularly elderly adults, is not as well documented. It is thought to help restore normal muscle to fat ratios. Growth hormone is an expensive and cautiously prescribed treatment.