Germline heterozygous AIP mutations are responsible for 20% of FIPA [10] and can be identified in 3-4% of unselected sporadic PAs [11, 12], 20.5% of childhood-onset PAs, 11.7% of pituitary macroadenomas in young patients (<30 years) [13], and around 7% of PAs diagnosed in patients under the age of 40 with no known family history of pituitary disease [11]. This evidence concerns the gene AIP and familial isolated pituitary adenoma.