GNAS and pseudohypoparathyroidism type 1A: On the basis of the presence or absence of AHO, urinary cAMP response to PTH infusion, resistance to other peptide hormones, and diminished in vitro Gsα activity, PHP is categorized into pseudohypoparathyroidism 1a (PHP1A; OMIM #103580), pseudohypoparathyroidism 1b (PHP1B; OMIM #603233), pseudohypoparathyroidism 1c (PHP1C; OMIM #612462), and pseudohypoparathyroidism 2 (PHP2; OMIM %203330) [3], [4], [5].