|
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.
Scientists estimate that about 3 out of every 1 million people develop acromegaly each year, and that 40 to 60 out of every 1 million people suffer from acromegaly at any given time.
Understanding the Pituitary Gland
The pituitary gland, sometimes called the master gland, plays a critical role in regulating growth and development, metabolism, and reproduction. The pituitary gland produces a number of key hormones, including:
- Prolactin, which stimulates the breast to produce milk during pregnancy. After delivery of the baby, a mother's prolactin levels fall unless she breast-feeds her infant. Each time the baby nurses, prolactin levels rise to maintain milk production.
- Growth hormone, which regulates growth.
- ACTH (corticotropin), which stimulates the adrenal glands to produce cortisol.
- Thyrotropin, which signals the thyroid gland to produce thyroid hormone.
- Luteinizing hormone (LH) and follicle-stimulating hormone (FSH), which regulate ovulation, estrogen, and progesterone production in women, and sperm formation and testosterone production in men.
The pituitary gland sits in the middle of the head in a bony box called the sella turcica. The eye nerves sit directly above the pituitary gland.
Understanding Growth Hormone
Growth hormone 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 gland. 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 gland 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.
Acromegaly is caused by prolonged overproduction of growth hormone (GH) by the pituitary gland. Common acromegaly causes include:
In over 90% of acromegaly patients, the acromegaly is caused by a benign (not cancerous) tumor of the pituitary gland called a pituitary adenoma (or growth hormone-secreting adenoma).
In a few patients, acromegaly is caused not by pituitary tumors, but by tumors of the pancreas, lungs, and adrenal glands. These tumors also lead to an excess of GH, either because they produce GH themselves or, more frequently, because they produce GHRH, the hormone that stimulates the pituitary to make GH.
The name acromegaly comes from the Greek words for "extremities" and "enlargement," and reflects one of the most common acromegaly symptoms: the abnormal growth of the hands and feet. Soft-tissue swelling of the hands and feet is often an early acromegaly symptom, 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 the spacing of the teeth increases.
Other common acromegaly symptoms include:
- Arthritis
- Fatigue and weakness
- Skin tags
- Sleep apnea
- Carpal tunnel syndrome
- Thick, coarse, oily skin
- Excessive sweating and skin odor
- Impaired vision
- Enlarged lips, nose, and tongue
- Deepening of the voice due to enlarged sinuses and vocal cords
- Headaches
- Impotence in men, also known as erectile dysfunction or ED
- Abnormalities of the menstrual cycle
- Breast discharge in women
- Enlargement of body organs, including the liver, spleen, kidneys, and heart.
(Click Acromegaly Symptoms to learn more about the symptoms of this condition.)
Acromegaly and Other Health Conditions
Acromegaly can lead to the development of other health conditions. The most serious health consequences of acromegaly are:
In order to make an acromegaly diagnosis, the doctor will ask a number of questions about a person's medical history, including: current symptoms, whether there is a family history of any medical problems, and any medicines the patient is taking. The doctor will also perform a physical exam, looking for any signs of acromegaly, and will order certain tests.
Tests used to help diagnose acromegaly and determine the acromegaly causes can include:
- Blood tests to measure GH and/or IGF-1 levels
- Glucose tolerance test
- Magnetic resonance imaging (MRI) scan
- Computed tomography (CT) scan.
(Click Diagnosing Acromegaly to read more about diagnosing this disorder.)
The goals of treatment for acromegaly are to:
- Reduce growth hormone (GH) production to normal levels
- Relieve the pressure that the growing pituitary tumor exerts on the surrounding brain areas to preserve normal pituitary function
- Reverse or improve the acromegaly symptoms.
Current options for acromegaly treatment include:
- Surgical removal of the tumor
- Drug therapy
- Radiation therapy of the pituitary.
(Click Acromegaly Treatment for a closer look at treatment options.)
Acromegaly Versus Gigantism
When growth hormone-secreting 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 development of excessive GH production in adults does not result in increased height. Prolonged exposure to excess GH before fusion of the growth plates, however, causes the increased growth of the long bones and increased height associated with gigantism.
Other Information on Acromegaly
Certain acromegaly topics in this article have a link to additional eMedTV articles that provide more in-depth information. Click the specific link to view the related acromegaly article.
|
|
Written by/reviewed by: Arthur Schoenstadt, MD
Last reviewed by: Arthur Schoenstadt, MD
|
Other Articles in This eMedTV Presentation
|
|
