Intriguingly, PRKAR1A mutations are not seen in sporadic somatotropinomas (i.e., those not associated with a germline mutation predisposing to adenoma formation), although somatic mutations in GNAS, as well as other genes (including USP8, BRAF,PIK3CA and TP53), are seen commonly in these tumors (46, 108–112). Here, PRKAR1A is linked to adenoma.