Normal ionized calcium, parathyroid hypersecretion, and elevated osteocalcin in a family with fluorosis.

Sera from five patients with skeletal fluorosis were investigated for total calcium, ionized calcium, phosphate, alkaline phosphatase, 25 hydroxyvitamin D (25 OHD), 1,25 dihydroxyvitamin D (1,25[OH]2D), parathyroid hormone, and osteocalcin concentrations. Total and ionized calcium concentrations were normal in four and subnormal in one, but PTH concentration was elevated in all five. The patient with a subnormal calcium concentration also had subnormal 25 OHD and 1,25(OH)2D concentrations and a supranormal PTH concentration. The remaining four had supranormal PTH concentrations despite normal total and ionized calcium concentration, and normal 25 OHD and 1,25(OH)2D levels. Osteocalcin concentration was markedly elevated in all patients, as was alkaline phosphatase activity. These observations show for the first time that patients with fluorosis have markedly elevated osteocalcin, a marker of osteoblastic activity, and that they may have significantly elevated PTH concentrations in the presence of normal total and ionized calcium concentrations.