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. Here, PLOD1 is linked to pseudohypoparathyroidism type 1A.