MEN1 and multiple endocrine neoplasia type 1: Only up to 5% of them are hereditary and can be caused, e.g. by MEN1 or aryl hydrocarbon receptor-interacting protein (AIP) gene mutations, and present as a part of multiple endocrine neoplasia type 1 (MEN1) or familial isolated pituitary adenoma (FIPA) syndromes (4, 5).