Tubular excretion of phosphate in Paget's disease of bone. Effect of pamidronate.

Two recent reports of phosphate diabetes in pagetic patients prompted us to evaluate urinary phosphate and its variations under pamidronate therapy in Paget's disease of bone. We also investigated whether Paget's disease is associated with phosphate diabetes. Urinary phosphate excretion was determined in 75 pagetic patients with a mean age of 72 years. None of the patients had received treatment during the six months preceding the evaluation. The 30 patients with clinical, laboratory test, and/or roentgenographic evidence of active Paget's disease were given intravenous pamidronate in a dosage of 60 or 120 mg. The control group was composed of thirty-seven age- and sex-matched subjects selected among patients admitted for degenerative bone or joint diseases. Phosphate and calcium levels were determined in blood and urine on two consecutive days in both cases and controls. The same assays were repeated six months after pamidronate therapy in the 30 patients with active Paget's disease. Phosphate diabetes was defined as a phosphate clearance above 20 ml/mn, a rate for tubular reabsorption of phosphate above 80%, and a ratio of the maximal rate for tubular reabsorption of phosphorus over the glomerular filtration rate (TmP04/GFR) below 0.80 mmol/l. As compared with controls, untreated cases had a nonsignificant increase in phosphate clearance (16.78 +/- 10.40 ml/mn versus 14.81 +/- 7.20 ml/mn), a significant decrease in tubular reabsorption of phosphate (83.41 +/- 5.57% versus 86.70 +/- 5.30%; p < 0.05), and a nonsignificant decrease in the TmP04/GFR ratio (0.93 +/- 0.14 mmol/l versus 0.98 +/- 0.15 mmol/l).(ABSTRACT TRUNCATED AT 250 WORDS)