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Hypopituitarism

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.

Adrenocorticotropic hormone

Also known as corticotropin, adrenocorticotropic 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

Prolactin stimulates the female breast to produce milk. A hormone produced by the posterior pituitary, called anti-diuretic hormone (ADH), controls the function of the kidneys.

Multiple hormone deficiencies

Deficiency of a single pituitary hormone occurs less commonly than deficiency of more than one hormone. Sometimes referred to as progressive pituitary hormone deficiency, or partial hypopituitarism, there is usually a predictable order of hormone loss. Generally, growth hormone is lost first; luteinizing hormone (LH) deficiency follows. The loss of follicle-stimulating hormone (FSH), thyroid stimulating hormone (TSH), and adrenocorticotropic hormones (ACTH) follows. The progressive loss of pituitary hormone secretion is usually a slow process that can occur over a period from months to years. Hypopituitarism, however, occasionally starts suddenly, with rapid onset of symptoms.

Panhypopituitarism

This condition represents the loss of all hormones released by the anterior pituitary gland. Panhypopituitarism is also known as complete pituitary failure.

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

Symptoms specific to this hormone deficiency include decreased interest in sex for women and infertility in women and men. Women may also have premature cessation of menstruation, hot flashes, vaginal dryness, and pain during intercourse. Women who are postmenopausal will not have such obvious symptoms, and may first present with headache or loss of vision. Men may also suffer sexual dysfunction as a result of gonadotropin deficiency. In acquired gonadotropin deficiency, both men and women may notice loss of body hair.

Thyroid stimulating hormone deficiency

A deficiency of TSH may produce intolerance to cold, fatigue, weight gain, constipation, and pale, waxy and dry skin. These symptoms can indicate thyroid hormone deficiency.

Adrenocorticotropic hormone deficiency

Symptoms of ACTH deficiency include fatigue, weakness, weight loss and low blood pressure. Nausea, pale skin, and loss of pubic and armpit hair in women may also indicate deficiency of ACTH.

Growth hormone deficiency

In children, growth hormone deficiency will result in short stature and growth retardation. Symptoms such as obesity and skin wrinkling may or may not show in adults; normal release of growth hormone normally declines with age.

Other hormone deficiencies

Prolactin deficiency is rare and is the result of partial or generalized anterior pituitary failure. When present, the symptom is absence of milk production in women. There are no known symptoms for men. Antidiuretic hormone deficiency may produce symptoms of diabetes insipidus, such as excessive thirst and frequent urination.

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.

Diagnosis and testing

Once the diagnosis of a single hormone deficiency is made (usually through blood tests, history taking for symptoms, and physical examination), it is strongly recommended that tests be conducted to rule out other hormone deficiencies. Diagnostic testing varies between men and women, because of differences in hormone levels between the sexes.

Multiple and general hypopituitarism tests

Nonspecific symptoms can indicate deficiency of one or more hormones. A thorough clinical history should be conducted through questioning by medical support staff and the physician. In general, diagnosis of hypopituitarism can be accomplished with a combination of dynamic and simple blood tests, as well as imaging exams. Most of these tests can be conducted in an outpatient laboratory or radiology facility. The magnetic resonance imaging (MRI) exam is the preferred imaging scan to study the suspicious region of the hypothalamus and pituitary glands, and is conducted by a radiographic technician. When MRI is not available, a carefully conducted computed tomography (CT)—also known as a computed axial tomography, or CAT scan—can be performed. Examination of the images produced by a CT can reveal a tumor or other mass that may be interfering with pituitary function. Tests for specific hormone deficiencies are as follows:

Gonadotropin deficiency

The detection of low levels of gonadotropin can be accomplished through simple blood tests that measure LH and FSH simultaneously with gonadal steroid levels. The combination of results can indicate to a physician if the cause of decreased hormone levels or function is attributable to hypopituitarism or some kind of primary gonadal failure.

Thyroid-stimulating hormone (TSH) deficiency

Laboratory tests measuring thyroid function can help the doctor to determine a diagnosis of TSH deficiency. The commonly used tests are T4 and TSH measurement, conducted simultaneously to determine the reserve, or pool, of TSH.

Adrenocorticotropic hormone deficiency

An insulin tolerance test (ITT) may be administered by laboratory technicians to determine if cortisol levels rise when hypoglycemia is induced. If they do not rise, there is insufficient reserve of cortisol, indicating an ACTH deficiency. If the ITT is not safe for a particular patient, a glucagon test offers similar results. A CRH (corticotropin-releasing hormone) test may also be given. It involves injection of CRH to measure, through regularly drawn blood samples, a resulting rise in ACTH and cortisol. Other tests that stimulate ACTH may be ordered.

Growth hormone deficiency

Growth hormone deficiency is measured through the use of insulin-like growth factor tests that measure growth factors that are dependent on growth hormones. Sleep and exercise studies may also be used to test for growth hormone deficiency, since these activities are known to stimulate growth hormone secretion. Several drugs can also induce secretion of growth hormone, and may be given in order to measure hormone response. The standard test for growth hormone deficiency is the insulin-induced hypoglycemia test. This test, however, does carry some risk from the induced hypoglycemia. Other tests include an arginine infusion test, clonidine test, and growth hormone releasing test.

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.

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.

Treatment

Treatment differs widely, depending on the age and sex of the patient, severity of the deficiency, the number of hormones involved, and the investigation of the underlying cause of the hypopituitarism. Immediate hormone replacement is generally administered to replace the specific deficient hormone. Patient education regarding the medical implications of the diagnosed hormone deficiency is encouraged to help patients manage the impact of their hormone deficiency on daily life. For instance, certain illnesses, accidents, or surgical procedures may elicit adverse complications or lesser outcomes, due to hypopituitarism. Treatment options for each of the hormone deficiencies are outlined below:

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 hypo-thalamic 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.

Adrenocorticotropic 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.

Treatment of multiple deficiencies and panhypopituitarism

The treatment of hypopituitarism is usually very straightforward, but must normally continue for the remainder of the patient's life. Some patients may receive treatment with GnRH, the hypothalamic hormone. In most cases, treatment will be based on the specific hormone deficiency. Patients with hypopituitarism should be monitored regularly to measure treatment effectiveness and to avoid overtreatment with hormone therapy. Radiation or surgical removal are options for treatment if the disorder is caused by a tumor or lesion. Successful removal of the mass may reverse the hypopituitarism. Even after its removal, however, hormone replacement therapy may still be necessary.

Prognosis

The prognosis for most patients with hypopituitarism is positive. As long as therapy is continued, many experience normal life spans. However, hypopituitarism is usually a permanent condition, and prognosis depends on the primary cause of the disorder. It can be potentially life threatening, particularly when acute hypopituitarism occurs as a result of a large pituitary tumor. The cause is not known. It is possible that increased morbidity and death are due to overtreatment with hormones. Recovery of pituitary function without medical intervention is preferred to lifelong hormone therapy.

Health care team roles

As with all conditions and diseases, patient education is critical and provided by medical support staff (i.e., nurses, nurse practitioners, physician assistants). Because of the delicate nature of several of the hormone deficiencies (e.g., growth and reproductive hormones), patients may experience low self-esteem and depression. Staff members who are in personal contact with patients during visits record any symptoms of stress or depression/anxiety, and should alert the physician. Patients should be advised on the benefits of mental health consultations or participation in support groups.

Coordination of care between mental health care providers, specialists and, in the instance of a surgical consult, surgical and hospital staff, may be required. This necessitates follow-up calls to the various health care providers who may become involved in the case. In some instances, patients will need to learn how to give themselves subcutaneous hormone injections, which requires teaching assistance from nursing staff or laboratory technicians. Alternatively, these patients may be required to make frequent office visits that require chart monitoring and assistance by office personnel. In this case, nursing and scheduling staff support is imperative to the avoidance of additional stress on the patient.

When the patient first presents with symptoms of hypopituitarusm, explanation of testing can ease the frustration of finding the diagnosis. The importance of patient compliance with a hormone regimen should be emphasized. In the case of deficiencies of more than one hormone, a daily treatment timetable may be needed (e.g., what time of day to take each hormone supplement). Thorough knowledge of the regimen is required by support staff members, and monitoring the regimen is important. Family members may be recruited to assist the health care team in making sure that compliance is optimal. Detailed chart management, thorough history taking at each subsequent visit, and the recording of notes on the smallest changes in a patient's symptoms are vital to a positive outcome.

Prevention

There is no known means of prevention of hypopituitarism apart from the prevention of damage/injury to the pituitary/hypothalamic areas of the head.

Resources

BOOKS

Conn, R.B., W.Z. Borer, and J.W. Snyder. Current Diagnosis. Philadelphia: W. B. Saunders Company, 1997.

ORGANIZATIONS

Alliance for Genetic Support Groups. 35 Wisconsin Circle, Suite 440. Chevy Chase, MD 20815-7015. 〈http://www.medhelp.org/geneticalliance/〉.

Human Growth Foundation. 7777 Leesburg Pike, Suite 202-South, Falls Church, VA 22043. 1-800-451-6434. 〈http://www.genetic.org〉.

OTHER

Health Answers. 〈http://www.healthanswers.com〉.