GNAS and obesity due to melanocortin 4 receptor deficiency: In addition to these skeletal features, patients with GNAS mutations on the maternally inherited allele develop pseudohypoparathyroidism type 1A (PHP1A), in which patients exhibit obesity and resistance to multiple hormones requiring Gαs-coupled receptors [such as parathyroid hormone (PTH), thyrotropin (TSH), luteinizing hormone (LH), follicle-stimulating hormone (FSH), calcitonin, glucagon, and growth hormone releasing hormone (GHRH)] [9, 13–18].