Vitamin D Metabolism in Patients Intoxicated with Ergocalciferol

Abstract

Vitamin D metabolites were measured on admission in 8 patients intoxicated with ergocalciferol (serum Ca 3.01-4.05 mmol/l) and also during the subsequent 2 mo. in 6 of the 8. Serum concentrations of 25-hydroxyergocalciferol, on admission, were grossly elevated in all patients (range 583-1843 nmol/l). Serum Ca concentration was related significantly only to the concentration of 25-hydroxyergocalciferol (P = 0.003). Concentration of 25-hydroxyergocalciferol in serum were significantly related to those of calciferol (P = 0.004). Elevated initial concentrations of 1,25-dihydroxycalciferol, mainly as 1,25-dihydroxyergocalciferol, were found in 7 of the 8 patients (range 179-313 pmol/l). The hypercalcemia in these patients may be explained by the action of 25-hydroxyergocalciferol at high concentration in competing for 1,25-dihydroxycalciferol receptors, thus exerting a biological effect per se, and also by increasing the synthesis of 1,25-dihydroxycalciferol through a mass-action effect on the renal 1.alpha.-hydroxylase.