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Acromegaly is a hormonal disorder that results when the pituitary gland produces excess growth hormone (GH). It most commonly affects middle-aged adults and can result in serious illness and premature death. Once recognized, acromegaly is treatable in most patients, but because of its slow and often insidious onset, it frequently is not diagnosed correctly.

The name acromegaly comes from the Greek words for "extremities" and "enlargement" and reflects one of its most common symptoms, the abnormal growth of the hands and feet. Soft tissue swelling of the hands and feet is often an early feature, with patients noticing a change in ring or shoe size. Gradually, bony changes alter the patient's facial features: the brow and lower jaw protrude, the nasal bone enlarges, and spacing of the teeth increases.

Overgrowth of bone and cartilage often leads to arthritis. When tissue thickens, it may trap nerves, causing carpal tunnel syndrome, characterized by numbness and weakness of the hands. Other symptoms of acromegaly include thick, coarse, oily skin; skin tags; enlarged lips, nose and tongue; deepening of the voice due to enlarged sinuses and vocal cords; snoring due to upper airway obstruction; excessive sweating and skin odor; fatigue and weakness; headaches; impaired vision; abnormalities of the menstrual cycle and sometimes breast discharge in women; and impotence in men. There may be enlargement of body organs, including the liver, spleen, kidneys and heart.

The most serious health consequences of acromegaly are diabetes mellitus, hypertension, and increased risk of cardiovascular disease. Patients with acromegaly are also at increased risk for polyps of the colon that can develop into cancer.

When GH-producing tumors occur in childhood, the disease that results is called gigantism rather than acromegaly. Fusion of the growth plates of the long bones occurs after puberty so that development of excessive GH production in adults does not result in increased height. Prolonged exposure to excess GH before fusion of the growth plates causes increased growth of the long bones and increased height.

What Causes Acromegaly?

Acromegaly is caused by prolonged overproduction of GH by the pituitary gland. The pituitary is a small gland at the base of the brain that produces several important hormones to control body functions such as growth and development, reproduction, and metabolism. GH is part of a cascade of hormones that, as the name implies, regulates the physical growth of the body. This cascade begins in a part of the brain called the hypothalamus, which makes hormones that regulate the pituitary. One of these, growth hormone-releasing hormone (GHRH), stimulates the pituitary gland to produce GH. Another hypothalamic hormone, somatostatin, inhibits GH production and release.

Secretion of GH by the pituitary into the bloodstream causes the production of another hormone, called insulin-like growth factor 1 (IGF-1), in the liver. IGF-1 is the factor that actually causes the growth of bones and other tissues of the body. IGF-1, in turn, signals the pituitary to reduce GH production. GHRH, somatostatin, GH, and IGF-1 levels in the body are tightly regulated by each other and by sleep, exercise, stress, food intake and blood sugar levels. If the pituitary continues to make GH independent of the normal regulatory mechanisms, the level of IGF-1 continues to rise, leading to bone growth and organ enlargement. The excess GH also causes changes in sugar and lipid metabolism and can cause diabetes.

How Common is Acromegaly?

Small pituitary adenomas are common. During autopsies, they are found in up to 25 percent of the U.S. population. However, these tumors rarely cause symptoms or produce excessive GH or other pituitary hormones. Scientists estimate that about 3 out of every million people develop acromegaly each year and that 40 to 60 out of every million people suffer from the disease at any time. However, because the clinical diagnosis of acromegaly often is missed, these numbers probably underestimate the frequency of the disease.

How is Acromegaly Diagnosed?

If a doctor suspects acromegaly, he or she can measure the GH level in the blood after a patient has fasted overnight to determine if it is elevated.

However, a single measurement of an elevated blood GH level is not enough to diagnose acromegaly, because GH is secreted by the pituitary in spurts and its concentration in the blood can vary widely from minute to minute. At a given moment, a patient with acromegaly may have a normal GH level, whereas a GH level in a healthy person may be five times higher.

Because of these problems, more accurate information can be obtained when GH is measured under conditions in which GH secretion is normally suppressed.

Physicians often use the oral glucose tolerance test to diagnose acromegaly, because ingestion of 75 g of the sugar glucose lowers blood GH levels less than 2 ng/ml in healthy people. In patients with GH overproduction, this reduction does not occur. The glucose tolerance test is the most reliable method of confirming a diagnosis of acromegaly.

Physicians also can measure IGF-1 levels in patients with suspected acromegaly. As mentioned earlier, elevated GH levels increase IGF-1 blood levels. Because IGF-1 levels are much more stable over the course of the day, they are often a more practical and reliable measure than GH levels. Elevated IGF-1 levels almost always indicate acromegaly. However, a pregnant woman's IGF-1 levels are two to three times higher than normal. In addition, physicians must be aware that IGF-1 levels decline in aging people and may be abnormally low in patients with poorly controlled diabetes mellitus.

After acromegaly has been diagnosed by measuring GH or IGF-1, imaging techniques, such as computed tomography (CT) scans or magnetic resonance imaging (MRI) scans of the pituitary are used to locate the tumor that causes the GH overproduction. Both techniques are excellent tools to visualize a tumor without surgery. If scans fail to detect a pituitary tumor, the physician should look for non-pituitary tumors in the chest, abdomen, or pelvis as the cause for excess GH. The presence of such tumors usually can be diagnosed by measuring GHRH in the blood and by a CT scan of possible tumor sites.

How is Acromegaly Treated?

The goals of treatment are to reduce GH production to normal levels, to relieve the pressure that the growing pituitary tumor exerts on the surrounding brain areas, to preserve normal pituitary function, and to reverse or ameliorate the symptoms of acromegaly. Currently, treatment options include surgical removal of the tumor, drug therapy, and radiation therapy of the pituitary.

Suggested Readings

Benefits versus risks of medical therapy for acromegaly. Acromegaly Therapy Consensus Development Panel. American Journal of Medicine 97(5):468-473, 1994.

Eastman RC, Gorden P, Glatstein E, Roth J. Radiation Therapy of Acromegaly. Endocrinology and Metabolism Clinics of North America 21(3):693-711, 1992.

Ezzat S, Forster MJ, Berchtold P, Redelmeier DA, Boerlin V, Harris AG. Acgromegaly. Clinical and Biochemical Features in 500 Patients. Medicine (Baltimore) 73(5):233-240, 1994.

Ezzat S. Living with acromegaly. Endocrinology and Metabolism Clinics of North America 21:753-760, 1992.

Jaffe CA; Barkan AL. Acromegaly. Recognition and treatment. Drugs 47(3):425-45, 1994.

Jaffe CA, Barkan AL. Treatment of acromegaly with dopamine agonists. Endocrinology and Metabolism Clinics of North America 21:713-735, 1992.

Krishna AY; Phillips LS. Management of acromegaly: a review. American Journal of Medical Science 308(6):370-375, 1994.

Melmed S. Acromegaly. New England Journal of Medicine 322:966-977, 1990.

Molitch ME. Clinical manifestations of acromegaly. Endocrinology and Metabolism Clinics of North America 21(3):597-614, 1992.

Other Resources

Pituitary Tumor Network Association
16350 Ventura Blvd., #231
Encino, CA 91436
(805) 499-9973
Fax: (805) 499-1523

This e-pub is not copyrighted. Readers are encouraged to duplicate and distribute as many copies as needed.

NIH Publication No. 95-3924
February 1995

e-text posted: 12 February 1998

Last updated February 12, 1998
Used with the permission of the copyright owner. All rights reserved.

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