Effect of Chloride on the Thyroid Gland.∗

Abstract

Hibbard has reported¹ hyperplasia of the thyroid with deficiency of colloid in rats given 2% of calcium chloride or 3% of sodium chloride in the drinking water. The diet consisted of pearled barley, which was low in iodine. Rats given distilled water without the added chloride had histologically normal thyroids. The results were interpreted as indicating that excess of chloride interferes with the utilization of minimal amounts of iodine in maintaining normal thyroid structure.

In the technique devised by the writer and his associates² for the quantitative measurement of the effects of iodine deficiency on the thyroid gland, judgment is based on 3 factors, viz., weight, dry matter and iodine content of the glands. In applying this method to the study of the effect of the chloride ion, the iodine deficient basal diet (diet 342) was varied by changing the salt content from 0 to 4%, and fed to parallel groups of young rats weighing 40-50 gm. for 6 weeks. Each group consisted of 6 animals, equally divided as to sex. The results are shown in Table I.

Rats receiving no salt made very por growth in comparison with the others, notwithstanding their food consumption per gram gain in weight was twice as great. This poor growth and high food consumption probably accounts for the higher dry matter and iodine content of the glands, since the diet is not entirely devoid of iodine. The normal values for rats of similar age in our colony are: thyroid weight 10 mg. per 100 gm. body weight, dry matter 32%, iodine on dry basis 0.200 %.³ When compared with these values, the rats of all groups had goiter, and increasing chloride up to the point where it began to retard growth did not affect the severity of the condition, with the possible exception noted above.