Heterozygous germline inactivating GNAS mutations on the maternally transmitted allele lead to type Ia or type Ic pseudohypoparathyroidism (PHP‐1a, PHP‐1c), which is associated with hormonal resistance to parathyroid hormone (PTH), thyroid‐stimulating hormone (TSH), gonadotropins (LH, FSH), growth hormone‐releasing hormone (GHRH), calcitonin, and some neurotransmitters of the central nervous system. This evidence concerns the gene GNAS and pseudohypoparathyroidism type 1A.