 However, the rest of the tissues will instead selectively display the defective gene, resulting in haploinsufficiency of the GNAS1 product in most tissues, and giving the phenotype of pseudohypoparathyroidism type 1a.As a result, there is also a normal response of urinary cAMP to PTH, and normal serum PTH.The diagnosis is based on the presence of the Albright hereditary osteodystrophy pseudotype but without the PTH resistance.