Magnesium Partition Studies in Graves ' Disease Andin

In a previous paper (1) we reported the results of determinations of total magnesium and ultrafiltrable magnesium in the serum of patients with hyperthyroidism. These findings were contrasted with those obtained in normal individuals, patients with autonomic imbalance, and patients with various types of muscular dystrophy. It was demonstrated that in normal individuals the percentage of the total serum magnesium which is non-diffusible did not exceed 22.1 per cent, with an average of 14.5 per cent, although Watchorn and McCance (2) report that, normally, approximately 25 per cent of the total serum magnesium is bound. The results obtained in patients with autonomic imbalance and various muscular dystrophies fell quite well within the normal range. In contrast to these groups, the patients with hyperthyroidism showed a very marked increase in the percentage of bound magnesium which varied from 21.5 to 61.6 per cent, with an average of 36.0 per cent. It was further pointed out that, after adequate treatment with iodine, there occurred a drop in the percentage of the nondiffusible magnesium fraction, which finally reached normal levels after subtotal thyroidectomy. No correlation was found between the individual basal metabolic rates and the percentage of bound magnesium. This is perhaps due to the fact that the metabolic rate was determined very shortly after admission to the hospital ward and hence may not represent the true basal rate. The increase in the percentage of non-diffusible magnesium in Graves' disease occurred entirely at the expense of the diffusible fraction, since the total serum magnesium in the patients with hyperthyroidism was approximately the same as that of the normal controls. In the present paper we are reporting further results of studies of magnesium partition in pa-