Here, we have analyzed the coding regions of GNAI1,GNAI2, and GNAI3 in a set of young sporadic somatotropinoma patients (n = 32; mean age of diagnosis 32 years) and familial index cases (n = 14), thus in patients with a disease phenotype similar to that observed in AIP mutation carriers. Here, GNAI1 is linked to growth hormone-producing pituitary gland neoplasm.