PTTG1 and non-functioning pituitary adenoma: Proto-oncogenes GNAS (guanine nucleotide-binding protein, alpha stimulating), PTTG (pituitary tumor-transforming gene 1), and tumor suppressor gene AIP (aryl-hydrocarbon receptor-interacting protein) are the most prominent genetic factors involved in pituitary tumorigenesis and have been implicated in the development of somatotropinomas and non-functioning pituitary adenomas (NFPA) (2).