Effect of Iodide, methimazole, and thyroxine on thyroidal accumulation of radioiodide in immature domestic fowl.

Accumulation of radioiodide by the thyroids of individual domestic fowl was measured with the technique described by T. F. Davison, J. G. Rowell, and J. Rea, [1981) J. Endocrinol. 89, 371-378). Radioiodide uptake was markedly decreased in birds given an excess of iodide in the drinking water (60 mg KI/liter) or injections of thyroxine (T4: 5 X 50 micrograms T4/kg body wt), in agreement with published findings. Treatment with a goitrogen (250 mg methimazole/liter drinking water) decreased 125I uptake for at least 8 days but thereafter uptake increased and this was accompanied by gross thyroidal enlargement. The results indicate that the thyroid partly compensates for goitrogenic inhibition.