Acromegaly is an extremely rare syndrome that results when the anterior pituitary gland produces excess growth hormone (GH) after epiphyseal plate closure at puberty. If GH is produced in excess prior to epiphyseal plate closure, the result is gigantism (or giantism). A number of disorders may increase the pituitary’s GH output, although most commonly it involves a 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 and fatal complications if unchecked. Because of its pathogenesis and slow progression, it is hard to diagnose in the early stages and is frequently missed for years until changes in external features, especially of the face, become noticeable.
https://checkorphan.org/diseases/acromegaly