AIP and pituitary gland adenoma: Loss-of-function mutations in the aryl hydrocarbon receptor-interacting protein gene (AIP) predispose to an autosomal dominant disorder with incomplete penetrance (20%–23%) associated usually with growth hormone-secreting pituitary adenomas leading to acromegaly or gigantism.1–3 To date, more than 100 different AIP variants have been identified, with the majority (75%) resulting in a missing or truncated AIP protein.2 3 A change in amino acid sequence due to missense variants could affect protein folding and stability4 and may alter the availability of protein–protein interaction sites.