In the current study, we have explored the action of wild-type human AIP (wtAIP), missense AIP variants identified in pituitary adenoma patients and AIP repression (siRNA or knockout) on the RET/PIT1/ARF/p53-apoptosis pathway, using well-characterized somatotroph cell lines, primary pituitary cultures, a new rat model of gigantism/acromegaly and a novel pituitary-specific Aip knockout mice. The gene discussed is RET; the disease is pituitary gland adenoma.