Acromegaly and gigantism

Acromegaly is characterized by excess growth hormone (GH) production, leadingto increased growth in bone and soft tissue and other disturbances throughout the body. In children, excess GH causes exceptional growth of long bones. This variant is called gigantism, because the additional bone growth causes unusual height. When too much GH is produced after a person has already reachedadult height, the disorder is called acromegaly. Acromegaly is rare, affecting approximately 50 out of every 1 million people. Both men and women are affected. Because symptoms occur gradually, most patients are not identified until they are middle aged.

GH is one of several hormones produced by the pituitary gland, which is located in the brain. Pituitary hormones are involved in many activities throughout the body, including growth regulation and reproductive functions. Under normal conditions, the pituitary's activity is directed by the hypothalamus, a small structure located at the base of the brain. In acromegaly, the pituitaryignores signals from the hypothalamus to stop releasing GH. As a result, bones, soft tissue, and organs throughout the body begin to enlarge, and the body changes its ability to process and use nutrients like sugars and fats.

The hands and feet of an individual with acromegaly grow larger. The jaw line, nose, and forehead also grow, and facial features are described as "coarsening." The throat and sinuses can swell, causing the voice to become deeper, and patients may also develop loud snoring. Hormonal changes cause heavy sweating, oily skin, and increased coarse body hair. The metabolism is also affected, as demonstrated by problems processing sugars from the diet (sometimes leading to diabetes), high blood pressure, increased calcium in the urine (possibly causing kidney stones), and increased risk of gallstones. Swelling of the thyroid gland in the neck may also be apparent.

People with acromegaly have more skin tags, or outgrowths on the skin, than normal. They may also develop growths, called polyps, in the large intestine which may become cancerous. Patients with acromegaly often suffer from headaches and arthritis. Swellings and enlargements throughout the body may press onnerves, causing local tingling or burning, and sometimes result in muscle weakness.

In 90% of patients, acromegaly is caused by a noncancerous tumor within the pituitary, called an adenoma. The adenoma may press on nearby structures within the brain, causing headaches and changes in vision. It may also interfere with the release of other pituitary hormones. These disruptions can change themenstrual cycle of women, decrease sexual drive in men and women, and causeabnormal production of breast milk in women. In rare cases, excess GH production in the pituitary is linked to tumors elsewhere in the body or abnormalities in the hypothalamus.

Because acromegaly produces changes slowly, diagnosis is often delayed. The characteristic coarsening of facial features is usually not recognized by family members, friends, or long-time family physicians. Often, the diagnosis issuspected by a new physician who sees the patient for the first time.

Demonstrating high levels of GH in the blood is not sufficient to diagnose acromegaly; however, other blood tests are useful. Normal patients show decreased GH production when given a large dose of sugar (glucose). Patients with acromegaly don't show this decrease and often show an increase. Magnetic resonance imaging (MRI) can be used to view the pituitary and to identify an adenoma. If no adenoma is found, the search for a tumor elsewhere begins.

Typically, the first step in treating acromegaly is surgical removal of a pituitary adenoma. While surgery can rapidly improve several symptoms, most patients also require medication. Bromocriptine (Parlodel) is a medication that can be taken by mouth, while octreotide (Sandostatin) must be injected every eight hours. Both of these medications help reduce GH production, but often are taken for life and have side effects. Patients who cannot undergo surgery may be treated with radiation therapy to shrink the adenoma. Radiating the pituitary may take up to 10 years, however, and may also injure/destroy normal parts of the pituitary.

Without treatment, patients with acromegaly will most likely die early because of the disease's effects on the heart, lungs, brain, or due to the development of cancer in the large intestine. With treatment, however, a patient withacromegaly may be able to live a normal lifespan.