PTH and Hypocalcemia: Pseudohypoparathyroidism type 1 (PHP1) is a disease caused by parathyroid hormone (PTH) resistance featuring hypocalcemia, elevated PTH level, unelevated urinary cyclic adenosine monophosphate (cAMP) after exogenous PTH injection, with/without Albright's hereditary osteodystrophy (AHO).