GNAS and pseudohypoparathyroidism type 1A: Because GNAS is paternally imprinted (silenced) in certain hormone target tissues, patients with Albright hereditary osteodystrophy with GNAS mutations on maternally inherited alleles often manifest resistance to multiple stimulatory G protein-coupled hormones (for example, parathyroid hormone (PTH), thyroid-stimulating hormone (TSH), luteinizing hormone (LH), follicular-stimulating hormone (FSH), and/or growth hormone-releasing hormone (GHRH)), a variant termed pseudohypoparathyroidism type 1a.