PTHLH and hypercalcemia disease: The laboratory assessments for the diagnosis of hypercalcemia include serum levels of calcium and ionized calcium, evaluation of PTH, PTHrP, and 1,25-dihydroxyvitamin D. In case of a paraneoplastic hypercalcemia, laboratory findings include elevated calcium levels, low-to-normal PTH levels, and often high PTHrP levels.