Acromegaly (/ˌækrəˈmɛɡəli, -roʊ-/; from Greek ἄκρον akron "extremity" and μέγα mega "big, large" (GEN μεγάλου)) 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).