PTH and Hypocalcemia: Patients with PHP type 1a (PHP1a) have PTH resistance (hypocalcaemia, hyperphosphataemia, elevated serum PTH, and a blunted increase in serum and urinary cyclic AMP [cAMP] and urinary phosphate following administration of PTH), in association with the features of Albright's hereditary osteodystrophy (AHO), which include short stature, obesity, subcutaneous calcifications, mental retardation, round facies, dental hypoplasia, and brachydactyly (i.e., shortening of the metacarpal bones, particularly the third, fourth, and fifth) [Thakker, 2011].