Acromegaly (pron-en?�kr??m???li; from Greek (Greek language) ????? akros "extreme" or "extremities" and ??????? megalos "large") is a syndrome that results when the pituitary gland produces excess growth hormone (human growth hormone) (hGH) after epiphyseal plate closure at puberty. A number of disorders may increase the pituitarys GH output, although most commonly it involves a GH producing tumor called pituitary adenoma, derived from a distinct type of cell (somatotrophs).

Acromegaly most commonly affects adults in middle age, and can result in severe disfigurement, serious complicating conditions, and premature death if unchecked. Because of its insidious pathogenesis and slow progression, the disease is hard to diagnose in the early stages and is frequently missed for many years, until changes in external features, especially of the face, become noticeable.

Acromegaly is often also associated with gigantism.