PTH and familial hypocalciuric hypercalcemia 1: Clinically, FHH1 is characterized by mild, non-progressive hypercalcemia, normal (in 80% of cases) or slightly elevated (in 20% of cases) serum PTH levels and hypocalciuria featured by low (<0.01) calcium-to-creatinine clearance ratio (CaCrCR) [19].