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What is Acromegaly?
Acromegaly is a hormonal disorder that develops when your pituitary gland produces too much growth hormone during adulthood. When this happens, your bones increase in size, including those of your hands, feet and face. Acromegaly usually affects middle-aged adults.
In children who are still growing, too much growth hormone can cause a condition called gigantism. These children have exaggerated bone growth and an abnormal increase in height.
Because acromegaly is uncommon and physical changes occur gradually, the condition often isn’t recognized immediately; sometimes not for years. If not treated promptly, acromegaly can lead to serious illness and even become life-threatening. However, available treatments for acromegaly can reduce your risk of complications and significantly improve your symptoms, including the enlargement of your features.
Causes of Acromegaly
Hormones are chemicals that control important body functions such as metabolism, growth and development, and reproduction. Growth hormone, like a number of hormones, is produced by the pituitary gland. It is one in a series of hormones that control tissue growth.
- The hypothalamus, a part of the brain, produces growth hormone-releasing hormone (GHRH). GHRH stimulates the pituitary to produce growth hormone and release it into the bloodstream.
- The hypothalamus produces another hormone called somatostatin that stops secretion of growth hormone.
- Growth hormone in the bloodstream stimulates the liver to produce another hormone called insulin-like growth factor 1 (IGF-1).
- IGF-1, in turn, promotes growth of bone and other tissues.
- Normally, levels of GHRH, growth hormone, somatostatin, and IGF-1 are tightly controlled by each other in a natural “feedback loop.” This feedback loop regulates supply of these hormones in the body. For example, a high level of IGF-1 in the blood suppresses secretion of GHRH and growth hormone in healthy people. Disruption of this and other similar hormone feedback loops causes many different medical problems, referred to as endocrine disorders.
- Levels of growth hormone and related hormones also are affected by sleep, exercise, stress, food intake, and blood sugar levels.
Excess growth hormone and IGF-1 in the blood cause most of the physical problems in acromegaly.
- Too much IGF-1 causes the bone growth that leads to changes in physical appearance and function.
- Itcauses thickening of soft tissues such as skin, tongue, and muscles. Enlargement of the tongue can lead to breathing problems and sleep apnea. Overgrowth of muscles can entrap nerves, causing pain syndromes such as carpal tunnel syndrome.
- Excess IGF-1 causes enlargement of organs such as the heart, which can result in heart failure and rhythm disorders.
- Excess growth hormone changes the way the body processes sugar and fats. This can cause diabetes and high levels of fats such as triglycerides in the blood. This in turn can lead to atherosclerosis and heart disease.
In most cases of acromegaly, the excess growth hormone isproduced by a tumor of the pituitary gland calledadenoma.
- Secretion of growth hormone by a pituitary tumoris not controlled by the feedback loop. The end result is an excess of IGF-1, which causesabnormal tissue growth.
- Many adenomas are caused by a genetic defect, but we do not know what causes the defect. These tumors do not seem to run in families.
- Adenomas are benign tumors, which means that they do not spread to other parts of the body.
- They can, however, grow to considerable size and cause problems by pressing on and invading surrounding tissues.
The remaining cases of acromegaly are caused by other types of tumors that secrete growth hormone or GHRH.
- These other tumors may be in the pituitary gland or elsewhere in the body.
- Acromegaly caused by excess growth hormone and acromegaly caused by excess GHRH have the same signs and symptoms.
Symptoms of Acromegaly
Symptoms of acromegaly may include any of the following:
- Body odor
- Carpal tunnel syndrome
- Decreased muscle strength (weakness)
- Decreased peripheral vision
- Easy fatigue
- Excessive height (when excess growth hormone production begins in childhood)
- Excessive sweating
- Joint pain, limited joint movement, swelling of the bony areas around a joint
- Large bones of the face
- Large feet (change in shoe size), large hands (change in ring or glove size)
- Large glands in the skin (sebaceous glands)
- Large jaw (prognathism) and tongue (macroglossia)
- Sleep apnea
- Thickening of the skin, skin tags
- Widely spaced teeth
- Widened fingers or toes, with swelling, redness, and pain
Other symptoms that may occur with this disease:
- Colon polyps
- Excess hair growth in females (hirsutism)
- Type 2 diabetes
- Weight gain (unintentional)
What happens in people with Acromegaly?
Acromegaly is caused by excessive production of growth hormone.
This usually occurs as the result of a benign (non-cancerous) brain tumour in the pituitary gland called an adenoma, but rare cases have been linked to tumours elsewhere in the body, such as in the lungs and pancreas.
Although acromegaly does very occasionally run in families, most adenomas are not inherited – they usually develop spontaneously as a result of a genetic change within a cell of the pituitary gland. This genetic change switches on a signal that tells cells in the pituitary gland to divide and secrete growth hormone.
The tumour almost never spreads to other parts of the body, but it may grow to more than 1cm in size and compress the surrounding nerves and normal pituitary tissue, which can affect the production of other hormones, such as thyroid hormones released from the thyroid gland.
How is acromegaly diagnosed?
If acromegaly is suspected, your doctor will do a blood test to check your level of IGF-1. High IGF-1 levels can mean that your levels of GH are also high.
Another way to diagnose acromegaly is with an oral glucose tolerance test. In this test, GH levels in the blood are measured after you drink sugar water. Normally, the sugar water will make the pituitary gland stop producing GH and blood levels drop. However, a GH-producing pituitary tumor will not stop making GH, so the levels of GH in the blood will not change.
The goals of therapyare to relieve and reverse the symptoms of acromegaly. This is done by normalizing production of growth hormone and IGF-1 and reducing the effects of the pituitary tumor on the surrounding tissues. A secondary goal is avoid damaging normal pituitary tissue.
At some time during the diagnosis or before beginning treatment, your health care provider will probably refer you to a specialist in hormonal disorders (endocrinologist)
Surgery to remove the pituitary tumor that is causing this condition often corrects the abnormal growth hormone. Sometimes the tumor is too large to remove completely. People who do not respond to surgery may have radiation of the pituitary gland.
Medications are used after surgery. Some patients are treated with medicines instead of surgery.
After treatment, you will need to see your health care provider regularly to make sure that the pituitary gland is working normally. Yearly evaluations are recommended.