STUDIES IN THE SUPPOSED GOITROGENOUS EFFECT OF TAP WATER IN HELSINKI

Abstract

The study reported here was performed in order to examine the tap water of Helsinki for its alleged goitrogenous effect. In a short-term, 24-hour experiment with rats, kept on an iodine-poor diet, no inhibition of the 4-hour 131I uptake, was noticed as compared with that of animals receiving physiological saline instead of tap water. Two similar groups of rats receiving 1 and 2 mg of mercazole in redistilled water showed a distinct blockage of the 4-hour uptake, which proved the effect of this substance. In a long-term experiment of 5 weeks'' duration there was no detectable difference in the body weight, thyroid weight and the 4-hour 131I uptake when the rats receiving tap water or distilled water to which 0.45% of sodium chloride was added were compared with each other. Replacement of tap water by a 10 mg% solution of mercaxole in redistilled water enlarged the thyroid to double its normal weight and increased the 131I uptake to approximately five times that of the controls. Thus the experiments failed to demonstrate any goitrogenous effect in the tap water of Helsinki. Changes similar to those produced by a long-term administration of mercazole, i.e. an enlargement of the thyroid and an increased thyroidal iodine uptake, have been shown to be due to milk collected from goitrous areas. The observations here reported confirm the importance of milk in the genesis of the goitre endemia of Helsinki. Attention is further called to the fact that a thyroidal enlargement combined with an increased thyroidal iodine uptake cannot always be taken as a sign of iodine deficiency because similar changes may be produced by the administration of goitrogens.