Three major aspects of calcium metabolism are susceptible to the use of isotope techniques and need investigation in patients with chronic renal disease. These are the problems of calcium absorption and endogenous fecal calcium loss, calcium-pool kinetics and soft-tissue calcium exchange, and bone mineral accretion and resorption. In all of these areas, the effects of therapy with vitamin D, dialysis, or homotransplantation need to be evaluated.
I will start with consideration of total-body calcium kinetics and the calculation of mineral accretion and resorption. Figure 1 presents the plasma specific-activity curve in a 51-year-old Negro man with chronic renal disease. Laboratory values were as follows: blood urea nitrogen (BUN), 100 mg/100 ml; creatinine, 20 mg/100 ml; calcium, 9.6 mg/100 ml; phosphorus, 6.0 mg/100 ml; and alkaline phosphatase 15.8 King-Armstrong units. The cross-hatched area in Fig 1 represents the plasmal calcium specific activity derived from a multilaboratory composite reference standard