GH1 and pituitary gland adenoma: ,2 In familial isolated pituitary adenomas, 15% to 30% of cases are associated with pathologic germline variants in the aryl hydrocarbon receptor–interacting protein (AIP) gene, a tumor suppressor gene located on chromosome 11q13.2, 3, 4, 5, 6 Germline AIP mutations are particularly associated with growth hormone- (GH) or mixed GH-prolactin–secreting pituitary adenomas.3, 4, 5, 6 Patients with AIP mutations are often men and have an aggressive clinical phenotype due to large invasive tumors.