The role of the thyroid gland in the period of growth is anabolic. The retention of calcium and nitrogen being used as a measure of the effect of thyroid, it was previously shown1 that maximal positive balances were obtained with a normal metabolic rate and that when the rate was depressed below or elevated above the normal there were accompanying diminutions in the retention of these two substances. In the case of nitrogen, it is doubtful that this effect is either large or specific. An increase in the absorption and oxidation of carbohydrate may be the primary result and a slight sparing of protein the secondary. There is, however, the added effect of increased appetite and intake of food, which results in a higher retention of nitrogen. In a long observation on cretins the negative balances observed when the metabolic rate was at its lowest were in part referable