THE EFFECT OF THIOURACIL ON THE COLLECTION OF RADIOACTIVE IODINE BY THE THYROID OF THE CHICK12

Abstract

Anatomic changes in the thyroid of the chick following the adm. of thiouracil did not appear until 5 days of treatment had elapsed. Inhibition of the capacity of the thyroid to collect injected radioactive I was shown to be at a maximum 1 hr. after the initial inj. of thiouracil. Thiouracil inhibited the collection of radio-active I by the thyroid of the normal chick, by the thyroid made hyperplastic by the inj. of thyrotrophic hormone and by the thyroid made hyperplastic by the adm. of thiouracil. The effect of thiouracil on the collection of radioactive I was largely dissipated within 24 hrs. The degree of inhibition produced by submaximal doses of thiouracil was a linear function of the logarithm of the dose. The effect of thiouracil on reducing the quantity of radioactive I collected by the thyroid may be the result of suppression of synthesis of I-containing compounds in the thyroid.