Hypophosphataemia after renal transplantation: relationship to immunosuppressive drug therapy and effects on muscle detected by 31P nuclear magnetic resonance spectroscopy

Abstract

Plasma phosphate values were examined in 72 renal transplant patients in a randomised trial of immunosuppression with azathioprine and prednisolone versus cyclosporin alone. From 21 to 77 days after transplantation, in patients with plasma creatinine concentrations of 75-150 mumol/l, mean plasma phosphate was 0.98 (SEM 0.04) mmol/l in cyclosporin-treated patients, compared with 0.65 (SEM 0.12) mmol/l in cyclosporin-treated patients receiving pulse methylprednisolone for rejection (P less than 0.003), and 0.68 (SEM 0.02) mmol/l in patients treated with azathioprine and prednisolone (P less than 0.001). There was no difference between the mean plasma creatinine of these groups of patients. A preliminary study by nuclear magnetic resonance spectroscopy of four patients with asymptomatic chronic hypophosphataemia showed reduced concentrations of intracellular phosphate in resting muscle, and further abnormalities developed on exercise. Thus, exogenous steroid administration is a major contributing factor of hypophosphataemia in the early post-transplant period. In addition chronic hypophosphataemia may be associated with reduced intracellular inorganic phosphate concentrations detectable by nuclear magnetic resonance spectroscopy, although these changes are not apparently associated with any clinical symptoms.