acromegaly, growth and metabolic disorder characterized by enlargement of theskeletal extremities. It is the result of overproduction of pituitarygrowth hormone (somatotropin) after maturity, caused by a tumour of thepituitary gland. Acromegaly is often associated with the abnormal growth in stature known as pituitary gigantism (seegigantism).

The onset of acromegaly is gradual. Hands and feet become enlarged; facial features are exaggerated as the jaw lengthens and the nose and forehead grow thicker; the skin thickens; and most internal organs enlarge. Headache, excessive sweating, muscle weakness, andhigh blood pressure are othermanifestations.

Acromegalic subjects may developcongestive heart failure, particularly whenblood pressure becomes high. At times, excessive overgrowth of bone and cartilage involves the joints and causes pain. The bones may become thin and porous—a condition known asosteoporosis.Diabetes mellitus appears in 20 to 40 percent of acromegalic subjects because excess growth hormone blocks the action ofinsulin. If thepituitary tumour enlarges, it can cause visual-field defects, blindness or paralysis of the eye muscles, and can injure the posterior pituitary gland or the hypothalamus. Also, hemorrhage into the tumour can cause sudden loss of vision.

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Acromegaly may be treated by surgical removal of the pituitary tumour or destruction of it by X-rayirradiation or liquid nitrogen. Rarely, the pituitary tumour willcease to secrete growth hormone because of a spontaneous hemorrhage or a blockage of the blood supply. Decreases in acromegalic manifestations and amelioration of diabetes mellitus have followed therapy with female hormones—estrogen or medroxyprogesterone—which reduce the secretion of growth hormone. For those treated by pituitarysurgery, irradiation, or other measures and for those who spontaneously develop deficits of gonadal, thyroidal, or adrenocortical hormones, replacement-hormone therapy is necessary.