Germline mutations of the Aryl-hydrocarbon Interacting Protein (AIP) gene, the gene responsible for some sporadic pituitary adenomas, and a subset (20%) of Familial Isolated Pituitary Adenoma (FIPA), have been detected in a few cases of sporadic PHPT and one MEN1 kindred [13–15]. The gene discussed is MEN1; the disease is pituitary gland adenoma.