A preliminary study of human calcium metabolism using long-term whole body tracer measurements.

Long-term bone calcium metabolism was measured using a whole body counter apparatus and the radioisotopes calcium-47 and strontium-85. Strontium was given with calcium in a single intravenous injection in order to estimate long-term retention of calcium. Calcium-47, with a short radio-active half-life, was measured directly for 20 days, and then indirectly from strontium retention for periods up to 200 days.The standard parameters of calcium transport were measured and, as well, a new parameter, calcium accretion to the fixed bone pool. These studies were carried out on 13 subjects, six of whom were selected "normals" and seven were patients with osteoporosis. Calcium accretion to the fixed bone pool, the new index of bone formation, varied from 100 to 210 mg. of calcium daily in normal subjects and from 70 to 340 mg./day in patients with osteoporosis. These values are one-third of those for the accretion to the total bone pool, the previously reported bone formation rate.