ACROMEGALY
What is Acromegaly?
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 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.
In over 90 percent of acromegaly patients, the overproduction of GH is caused by a benign tumor of the pituitary gland, called an adenoma. These tumors produce excess GH and, as they expand, compress surrounding brain tissues, such as the optic nerves. This expansion causes the headaches and visual disturbances that are often symptoms of acromegaly. In addition, compression of the surrounding normal pituitary tissue can alter production of other hormones, leading to changes in menstruation and breast discharge in women and impotence in men.
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.
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 lessen the symptoms of acromegaly. Currently, treatment options include surgical removal of the tumor, drug therapy, and radiation therapy of the pituitary.
» top