GNAS gene encodes the stimulatory alpha subunit of a protein complex called a guanine nucleotide-binding protein (G protein). G proteins are involved in signal transduction, the process of transmitting signals from a variety of stimuli outside a cell to its interior. The G protein containing the GNAS encoded subunit is responsible for stimulating the activity of the adenylate cyclase enzyme. As adenylate cyclase is believed to play a key role in signaling pathways that help regulate osteogenesis and hormone production, the G protein is essential for the regulation of these processes.

GNAS is associated with several disorders, namely: somatic acromegaly, ACTH-independent macronodular adrenal hyperplasia, somatic mosaic McCune-Albright syndrome, progressive osseous heteroplasia, pseudohypoparathyroidism (types Ia, Ib and Ic) and pseudopseudohypoparathyroidism. 

GNAS is a complex imprinted locus and the presence of alternative promoters as well as alternative splicing results in multiple isoforms of the protein. The Gs-alpha transcript, responsible for encoding the alpha subunit of the stimulatory guanine nucleotide-binding protein, is expressed biallelically in most tissues of the body. The remaining GNAS transcripts are all expressed exclusively from either the paternal or maternal allele. Inactivating loss-of-function mutations in the GNAS1 gene result in pseudohypoparathyroidism IA, pseudopseudohypoparathyroidism, and progressive osseous heteroplasia, while activating gain-of-function mutations in the GNAS1 gene result in McCune-Albright syndrome, polyostotic fibrous dysplasia, and various endocrine tumors.