1913.] Metabolism in its Relation to the Thyroid Gland. 



559 



thyroid administration on a diet relatively rich in protein and poor in 

 carbohydrates, while in Experiment 2 the diet was poor in protein and rich 

 in carbohydrates. There is in both cases a marked rise in the nitrogen output 

 due to an increased excretion of urea and ammonia, so that the percentage 

 distribution of the urea- and ammonia-nitrogen remains practically the same. 

 On the protein-rich diet there is also a distinct increase in the excretion of 

 uric acid, and a slight increase in the excretion of creatinin, effects which are 

 completely absent on the protein-poor diet. It is further interesting to note 

 that no creatin is excreted when the thyroid is administered on a carbo- 

 hydrate-rich diet. 



Experiment 3 shows that withdrawal of carbohydrates from the diet is 

 accompanied by a rise in the nitrogen-output which is due to an increased 

 excretion of urea and ammonia. It is interesting to note that in spite of the 

 fact that the subject of the experiment had been on a creatin- and creatinin- 

 free diet for 24 hours before the beginning of the experiment, creatin was still 

 being excreted and the creatinin excretion was above the normal for that 

 person. There is a distinct increase in the excretion of creatin as the result 

 of the withdrawal of carbohydrates from the diet. 



A more detailed study of the effect of thyroid feeding on protein metabolism 

 is at present being carried out by one of us. Here it is sufficient to point 

 out that the similarity in the distribution of the urinary nitrogen in the two 

 conditions (thyroid feeding and withdrawal of carbohydrates) suggests that 

 the action of the thyroid hormone on protein metabolism is effected partly, at 

 any rate, through its action on carbohydrate metabolism. 



It would follow, too ; that endogenous protein metabolism is many sided, 

 more so than it has been supposed to be. There is that generally recognised 

 form of endogenous protein metabolism, which is represented by the formation 

 of creatinin and which is not very susceptible to the influence of the thyroid 

 hormone. But there is yet another form of endogenous protein metabolism, 

 quite independent of the former, which is under the influence of the thyroid 

 gland and which would appear to have some specially close relation to the 

 metabolism of carbohydrates. 



General Discussion. 



The most remarkable feature of the condition induced by thyroid feeding 

 lies in the fact that the marked inhibition of the glycogenic function of the 

 liver is not accompanied by a glycosuria or, at any rate, a very marked 

 lowering of the tolerance for glucose, as the generally accepted view of 

 carbohydrate metabolism would lead one to expect. This absence of any 

 marked influence on the more obvious features of carbohydrate metabolism 



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