Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant disorder caused by MEN1 gene mutations, typically involving primary hyperparathyroidism (PHPT), pancreatic neuroendocrine tumors (PanNETs), and/or pituitary neuroendocrine tumors (PitNETs). Here, MEN1 is linked to primary hyperparathyroidism.