Acromegaly overview

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

Acromegaly (from Greek akros "extreme" or "extremities" and megalos "large" - extremities enlargement) is a hormonal disorder that results from too much growth hormone in the body. The pituitary gland, a small gland in the brain, makes growth hormone. In acromegaly, the pituitary produces excessive amounts of growth hormone, usually from a benign, or noncancerous, tumor on the pituitary gland. These benign tumors are called pituitary adenomas.

Acromegaly most commonly affects middle-aged adults and can result in serious illness and premature death. Because of its insidious onset and slow progression, the disease is hard to diagnose in the early stages and is frequently missed for many years. Common symptoms include slow enlargement of jaw, hands, feet, and coarsening of facial features. The most serious health consequences of acromegaly are type 2 diabetes, high blood pressure, increased risk of cardiovascular disease, and arthritis. Patients with acromegaly are also at increased risk for colon polyps, which may develop into colon cancer if not removed.

When growth hormone-producing adenomas occur in childhood, the disease that results is called gigantism rather than acromegaly. A child’s height is determined by the length of the so-called long bones in the legs. In response to growth hormone, these bones grow in length at the growth plates—areas near either end of the bone. Prior to puberty, excessive growth hormone exposure causes increased height. Growth plates fuse after puberty, so the excessive growth hormone production in adults does not affect height.

Historical Perspective

Acromegaly was first described by DR. Johannes Wier in 1567. Dr. Verga reported a case of acromegaly in 1864 and it was a case of a patient with a disproportionate big face. Through 1877 to 1900s, many physicians reported cases of acromegaly. In 1970, Dr. Besser used bromocriptine in the treatment of acromegaly and it showed a remarkable improvement in the patients. In 1988, FDA approved for the octreotide as a treatment to acromegaly.

Classification

There is no classification system established for acromegaly

Pathophysiology

Acromegaly is caused by prolonged overproduction of growth hormone by the pituitary gland. 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. One of the hormones in the GH axis is growth hormone-releasing hormone (GHRH), which stimulates the pituitary gland to produce GH.

Secretion of GH by the pituitary into the bloodstream stimulates the liver to produce another hormone called insulin-like growth factor I (IGF-I). IGF-I is what actually causes tissue growth in the body. High levels of IGF-I, in turn, signal the pituitary to reduce GH production.

The hypothalamus makes another hormone called somatostatin, which inhibits GH production and release. Normally, GHRH, somatostatin, GH, and IGF-I 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-I continues to rise, leading to bone overgrowth and organ enlargement. High levels of IGF-I also cause changes in glucose (sugar) and lipid (fat) metabolism and can lead to diabetes, high blood pressure, and heart disease.

Causes

Acromegaly is caused by prolonged overproduction of growth hormone, most commonly by the pituitary gland by benign tumors called pituitary adenomas. It can also be caused by non-pituitary tumors that make growth hormone or growth hormone releasing hormone, but this is very rare.

Epidemiology and Demographics

Acromegaly is rare with an estimated prevalence of 36–60 cases per million with an annual incidence of 3–4 per million. Acromegaly is often recognized and diagnosed in middle-aged men or women but can occur at any age. The disease is equally distributed between both sexes.

Screening

Screening for acromegaly in the general population is not recommended.

References

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