Mutations of the gene for the aryl hydrocarbon receptor-interacting protein in pituitary adenomas

Heterozygous germline mutations in the gene encoding the aryl hydrocarbon receptor-interacting protein (AIP) were first described in two Finnish families with pituitary adenomas. The gene is involved in about 15% of familial isolated pituitary adenomas (FIPA), in about 50% of cases of familial acromegaly and in a small proportion of acromegalic patients with sporadic presentation. This review describes the genetic and clinical features of published patients with AIP, with either familial or sporadic pituitary tumors. A genotype-phenotype correlation is proposed: patients with AIP mutations resulting in a truncated protein are significantly younger than those bearing a mutation which preserves the structure of the C-terminal end of the protein (22.7 +/- 9.6 vs. 29.8 +/- 10.9 years). Pituitary tumors linked to AIP mutations are almost exclusively somatotropic (87.5%, n = 56/64) or lactotropic (9.4%, n = 6). Patients with AIP mutations are mostly men (70%, 44 M/19 F), suffer macroadenomas (97%) and are younger at diagnosis (24.4 +/- 10.5 years) than unselected patients with pituitary tumors. Thus, AIP is involved in the development of pituitary tumors, especially involving the somatomammotroph lineage. Genetic testing could be discussed for FIPAs and in young acromegalic patients with a sporadic presentation. Functional studies are needed to understand AIP-induced tumorigenesis.