560 Carbohydrate Metabolism in its Relation to the Thyroid Gland. 



masks the relation which exists between the thyroid secretion and the carbo- 

 hydrate metabolism, and has no doubt been the reason why this relation, 

 although so frequently suspected, has not been demonstrated before. The 

 fact that the glycogenic function of the liver may be so completely in 

 abeyance, without producing any correspondingly marked effect on the 

 tolerance for glucose, leads one to conclude that these two aspects of carbo- 

 hydrate metabolism are independent of each other to a far greater extent than 

 is generally supposed. Further investigations on this point are in progress. 



The constancy with which the effect of the thyroid hormone on the liver 

 glycogen is produced suggests this as a suitable test for the investigation of 

 the relations which the thyroid is supposed to have to other internally 

 secreting glands. 



In conclusion it may be pointed out that the effects described in this 

 paper are produced by the administration of thyroid gland to normal animals 

 and represent therefore the conditions induced by a hypersecretion of the 

 gland. It does not necessarily follow, although it is possible, that the thyroid 

 hormone, in the amounts in which it is poured out into the blood in a normal 

 animal, also has an inhibiting influence on carbohydrate metabolism. For it 

 is a well known fact that physiologically active substances, which in large 

 doses have a paralysing effect, produce a stimulating effect in smaller doses. 



Summary. 



When small amounts of fresh thyroid gland are administered for two or 

 three days to rats or cats fed on a carbohydrate-rich diet, the liver will be 

 found to contain only traces of glycogen. 



This effect is due to an inhibition of the glycogenic function of the liver, 

 not to an increased utilisation of carbohydrates. It is not accompanied by 

 glycosuria, and other experiments on dogs, not recorded in this paper, show 

 that the tolerance for glucose is only slightly diminished by thyroid feeding. 



The action of the thyroid secretion on protein metabolism is effected partly 

 through its action on carbohydrate metabolism, for the distribution of the 

 nitrogenous constituents of the urine after thyroid feeding is very similar to 

 that observed after withdrawal of carbohydrates from the diet or in disturb- 

 ances of carbohydrate metabolism. 



It is specially pointed out that the condition of the carbohydrate metabolism 

 produced by thyroid feeding is unique. The bearing of these observations on 

 current conceptions of protein and of carbohydrate metabolism is briefly 

 discussed. 



The expenses of this research were defrayed by grants from the Moray 

 Fund. 



