GNAS and fibrous dysplasia: The activating Gsα mutations lead to endocrine tumors, McCune–Albright syndrome (MAS), and fibrous dysplasia of bone; the heterozygous loss-of-function in GNAS cause Albright hereditary osteodystrophy (AHO), a syndrome characterized with short stature, brachydactyly, developmental delay or mental deficits, facial defects such as orbital hypertelorism and depressed nasal bridge.