Hyperparathyroidism, glucose tolerance and platelet intracellular free calcium in chronic renal failure

Disturbance in the vitamin D/parathyroid hormone (PTH) axis may be important in the pathogenesis of glucose intolerance and insulin resistance in uraemia. To investigate possible relationships between hyperparathyroidism, intracellular free calcium ([Ca²⁺]₁), and glucose tolerance in chronic renal failure, we measured serum intact PTH (l-PTH) by two-site immunometric assay, platelet [Ca²⁺]₁ using the fluorescent indicator fura-2, and plasma glucose and insulin after 14 h overnight fast and at 30, 60 and 120 min following a 75 g oral glucose load, in 18 chronic haemodialysis patients with elevated serum l-PTH. Calcitriol (1 μg) was administered parenterally at the end of each dialysis session for four weeks. This significantly decreased serum l-PTH (p<0.001) and platelet [Ca²⁺], (p<0.01). Uraemic patients initially showed marked glucose intolerance, with increased area below the glucose curve compared to healthy controls, but after 4 weeks of calcitriol treatment, this effect was significantly decreased, and there was a significant rise in the area under the insulin curve after glucose load. The insulinogenic index also increased significantly after calcitriol treatment.