Brit.J. industr. Med., i966, 239 3I3 Hypocalcaemia in Experimental Cadmium Poisoning

Renal stones, hypercalciuria, and radiological bone changes have been found in workers exposed to compounds containing cadmium. In the present experiments the effect of cadmium chloride injections on the serum calcium levels of rabbits has been studied. Repeated subcutaneous injections over a period of two weeks at a dosage of up to 0o04 mmole/kg. body weight produced a slight but consistent fall in the serum calcium level by about 2 mg./ioo ml. Vacuolation of the parathyroids occurred in a few animals. Single intravenous injections of cadmium chloride, at dosages of O OI, O O15, and 0o02 mmole/kg. body weight, produced falls of between 2 and 4 mg./I00 ml. in the serum calcium level measured six hours later. In animals which survived the level was still low at 24 hours, after which the serum calcium returned to normal levels. The degree of hypocalcaemia was proportional to the dose of cadmium used. It is suggested that this fall in the serum calcium level may have been due to increased renal excretion. Industrial workers exposed to cadmium (Cd) have a high incidence ofrenal calculi; Friberg (I959) estimated that about one quarter of the men engaged in the Swedish accumulator industry had been found to have a history of urinary stones. A more exact estimate of the incidence of nephrolithiasis was given by Ahlmark, Axelsson, Friberg, and Piscator (I960) who showed that the incidence of nephrolithiasis rose with the duration of exposure to cadmium. In men exposed to cadmium for between six and I0 years, I2 % had renal stones, but in those exposed for more than I5 years the incidence rose to over 40%. Quite apart from cadmium poisoning, renal calculi are common, and hypercalciuria has been recog-nized as one of the causes of calculi since the observations of Flocks (1939). However, the only detailed study of the urinary calcium excretion of men exposed to cadmium is that of Kazantzis, Flynn, Spowage, and Trott (I963), who found levels in excess of 300 mg./day in seven out of I2 subjects; the serum calcium levels were normal. Previous to this there is no published account of disorders of calcium metabolism in cadmium poisoning although radiological changes in bone resembling those of Milkman's syndrome have been found (Nicaud