Mutations in the aryl-hydrocarbon receptor (AHR) interacting protein (AIP) and p27KIP1 encoding gene CDKN1B have recently been associated with familial forms of acromegaly [18]–[20], though no evidence has been produced to support a role for these genes in sporadic endocrine neoplasms other than pituitary adenoma [21], [22], or in the higher cancer risk seen in acromegalic patients [23]. The gene discussed is AHR; the disease is acromegaly.