The effect of butylated hydroxytoluene (BHT) on the rat thyroid.

Butylated hydroxytoluene (BHT) was given to rats in the diet at levels of 500 and 5000 ppm for different periods of time up to 90 days. Iodine uptake by the thyroids, the half life of thyroxine and the weights of liver and thyroid were determined when 5000 ppm BHT was given in commercial or semisynthetic diets containing different amounts of iodine. Iodine uptake was significantly increased in those animals given BHT into the diet, but the half-life of thyroxine was unchanged or slightly prolonged. Thyroid weight was enhanced at both 500 and 5000 ppm BHT, while liver weight was increased ony in the latter. No explanation of the pathogenesis of the effect can be suggested.