Genetic defects affecting GNAS can cause several human diseases such as Pseudopseudo hypoparathyroidism (PHP, MIM:612462, 603233, 103580 ), end-organ resistance to parathyroid hormone (PTH, MIM: 612463), progressive osseous heteroplasia (POH, MIM: 166350). The gene discussed is GNAS; the disease is pseudopseudohypoparathyroidism.