Effect of thyroidectomy on circulating thyroid hormones in dogs administered insulin.

In the blood of intact dogs, insulin increases the labelled thyroid hormones (PBI) by about 30% and doubles the T3 level. In athyreotic insulin-administered dogs, the circulating T4 and T3 remain at more or less unvarying values, the plasma disappearance slope of radiothyroxine is not altered. Such data suggest that without the thyroid gland, insulin has no action on the level of the blood thyroid hormones.