PTH and congenital adrenal hyperplasia: However, other non-CAH genetic etiologies have been gradually established, such as NR5A1/SF-1, NROB1/DAX-1, ABCD1 and PEX1. The GNAS gene encodes the alpha-subunit of the G protein (Gsα) which mediates the signalling of numerous peptide hormones such as parathyroid hormone (PTH), thyroid stimulating hormone (TSH), growth hormone–releasing hormone (GHRH), adrenocorticotropic hormone (ACTH), and gonadotrophins.