Studies on a thyroid-depressing factor of renal origin in the rat

Abstract The weight of the thyroid glands of rats was increased, and uptake of 131 I reduced, when a factor from donor rat kidneys was injected ip for 6 days. Stepwise fractionation of rat renal homogenates by ultracentrifugation yielded vasodepressor, vasoneutral and vasopressor fractions. Only the vasoneutral fraction (31,500 g , 30 min) contained the thyroid-depressing factor (TDF). Similar fractions of muscle and liver contained no TDF. Results of other studies using bovine thyroid slices suggest that TDF may act at the level of the thyroid gland by inhibiting some aspect of the concentrating mechanism for iodide. Thus drugs or treatments affecting the kidney may indirectly influence the function of the thyroid gland.