Mechanism for bone disease found in inhabitants environmentally exposed to cadmium: decreased serum 1 alpha, 25-dihydroxyvitamin D level.

To investigate the mechanism for bone disease caused by exposure to cadmium serum samples were collected from 5 itai-itai disease patients, 36 Cd-exposed residents with renal tubular damage and 17 non-exposed individuals and analyzed for 1 alpha,25-dihydroxyvitamin D[1 alpha,25(OH)2D], parathyroid hormone, beta 2-microglobulin, calcium and inorganic phosphorus. Measurement of percentage tubular reabsorption of phosphate (%TRP) were performed only on the Cd-exposed subjects. Serum 1 alpha,25(OH)2D levels were lower in itai-itai disease patients and cadmium-exposed subjects with renal damage than in non-exposed subjects. Parathyroid hormone and beta 2-microglobulin concentrations in serum were higher in the Cd-exposed subjects. Decrease in serum 1 alpha,25(OH)2D levels were closely related to serum concentrations of parathyroid hormone, beta 2-microglobulin and %TRP. This study suggests that cadmium-induced bone effects were mainly due to a disturbance in vitamin D and parathyroid hormone metabolism, which was caused by the cadmium-induced kidney damage.