Mutations of the GNAS1 gene, which is located on chromosome 20q13.11 and encodes the alpha-subunit of the stimulatory GTP-binding protein, have been identified in patients with pseudohypoparathyroidism type Ia (PHPIa) and pseudopseudohypoparathyroidism (PPHP).
Mutations in exon 7 of the GTP-binding protein Gs alpha were not a common cause of pseudohypoparathyroidism with Albright's hereditary osteodystrophy in Japanese.