Adult-onset idiopathic phosphate diabetes. II. Time-course of clinical, laboratory test, and bone mineral density abnormalities under combined phosphate and calcitriol therapy.

Study Objective: to investigate the time-course of clinical, laboratory test, and bone mineral density abnormalities in patients with mild phosphate diabetes treated for at least one year with calcitriol, 0.5 to 1.5 micrograms, and oral phosphate, 788 to 2300 mg per day, in three divided doses.

Patients And Methods: we studied eight patients with mild phosphate diabetes defined as a rate for tubular reabsorption of phosphate of less than 18% with a maximal rate for tubular reabsorption of phosphate (Tm) of less than 0.77 in the absence of any detectable cause of secondary tubular disease. Treatment efficacy was evaluated on the basis of pain severity, pain-related functional disability, serum phosphate and calcium levels, maximal rate for tubular reabsorption of phosphate, and dual-photon absorptiometry-measured bone mineral density.

Results: three patients experienced complete relief of pain and fatigue and were able to resume their normal activities. Partial relief was seen in two other patients. The three remaining patients had no response to treatment. Renal colic occurred in one patient. None of the patients developed hypercalcemia.