Abstract
Prolonged intake of large doses of sodium iodide, with no restriction of sodium chloride, definitely caused thyroid enlargement in mice. In hypophysectomized mice, however, thyroid weight was not significantly increased by excess iodide regardless of the long duration of iodide treatment. An increase in pituitary TSH content and a slight increase of plasma TSH concentration were observed in the iodide treated mice. To clarify which thyroid tissue components were responsible for the increase in gland weight, qualitative and quantitative measurements were performed on histological sections and also nucleic acids and protein contents were determined. The biosynthetic capacity Histological observations revealed that the goiter induced by iodide was due to an increase of colloidal material. Marked accumulation of luminal thyroglobulin and an enlargement of follicle size were noticed. This observation was in accord with the quantitative determination of nucleic acids and protein. A decrease of DNA per tissue weight and an increase of RNA/DNA ratio and protein contents were observed in goitrous thyroid. From the experiments with 131I, no detectable altering of the pattern of hormone synthesis, was found in goitrous thyroid. Plasma BE 131I level was, however, markedly decreased. Furthermore, the inhibitory effect of thiouracial was antagonized by concurrent administration of iodide. The effect of large amounts of iodide on the mouse thyroid is discussed in this paper, on the basis of the experimental results obtained.
