Vitamin A and hyperparathyroid bone disease in uremia.

The possible contribution of hypervitaminosis A to bone disease in uremia was examined in 50 dialysis-treated patients with end-stage chronic renal failure. None of the patients received dietary supplements of vitamin A. In common with previous investigations, plasma concentrations of total vitamin A and the retinol-binding protein (RBP) were increased in patients, but the molar ratio of vitamin A to RBP was significantly lower than control values. A significant correlation was noted between concentrations in plasma of vitamin A and RBP. No significant relationship was found between vitamin A or the vitamin A/RBP ratio, and the measured biochemical, radiographic, or histological indices of hyperparathyroidism and bone resorption. We conclude that the elevated plasma values of vitamin A in uremia are largely attributable to the high concentrations of RBP and do not contribute significantly to the pathogenesis of renal osteodystrophy.