Behavior of the Thyroid Toward Elements of the Seventh Periodic Group

Abstract

In order further to test our hypothesis that the elements of group VII are selectively filtered from the blood and concentrated by the thyroid gland, rats were injected with Mn⁵⁴, Br⁸² and Tc⁹⁹. The distribution of these nuclides in tissues was determined 2 hours after administration. The thyroidal concentration of Mn⁵⁴ was about 10 times that of serum, of Br⁸² 1.3 times that of blood and of Tc⁹⁹ 11–30 times that of blood. These results together with those previously reported by us and by others show that ions of all group VII elements are concentrated by the thyroid, though to a varying extent. A study of the effect of stable seventh group ions on the uptake of Mn⁵⁴, Br⁸², I¹³¹ and Re¹⁸⁶ shows that large amounts of F^–, Mn⁺⁺ and Br^– have little influence while even small quantities of I^– or of Re⁺⁺ markedly lower the thyroidal uptake of the heavier ions. Only a slight affinity of the thyroid for F^–, Mn⁺⁺, Br^– is thus indicated, while that for I^– and Re⁺⁺ is far greater. This conclusion is substantiated by another type of experiment in which pairs of these nuclides were administered simultaneously and the fraction of each taken up by the thyroid determined. The affinity of the thyroid for Te, I and Re proved to be roughly equal and much larger than for Mn or Br. Unlike other group VII elements Mn accumulates in tissues of endodermal origin to an even greater extent than in the thyroid.