HYPOTHYKOIDISM 431 



the basal metabolism is so constant that Henry Plummer could estimate 

 that 1 mg. thyroxin increases by 2 per cent the basal metabolism of an 

 adult weighing approximately 150 pounds. Apparently the sole objection 

 to the clinical use of thyroxin is its present expense. 



Excellent dried thyroid extracts are now obtainable which contain a 

 known quantity of iodin (usually 0.2 per cent) therefore a fairly constant 

 amount of thyroxin. With the best of such preparations the general expe- 

 rience has been good. Their use is entirely justifiable and their cheapness 

 recommends them for dispensary and poorer practice. The oral dosage 

 ranges from % gr. in light to 5 or 6 gr. per diem in severe cases. The 

 general tendency is to administer smaller doses than formerly. The cor- 

 rectness of this view has been established by recent studies of the basal 

 metabolism. 



Metabolic Control of Treatment. The modern basal metabolic rate 

 determinations have one of their chief uses in the control of thyroid treat- 

 ment. Succeeding the preliminary studies by DuBois, Means and Aub, 

 Plummer, Kowntree, Janney and others, this method is in process of 

 general introduction at the present writing (1921). In hypothyroidism, 

 the basal metabolic rate rises promptly on thyroid medication, reaching 

 in a few days to a fortnight the normal when the dosage has been cor- 

 rectly chosen. Aside from the accompanying symptoms of thyrotoxicosis, 

 an overdose of thyroid substance will elevate the gaseous exchange to above 

 the normal. Conversely on insufficient dosage the rate will fail to reach 

 this level. If technically accurate metabolism determinations are made at 

 regular intervals in carrying out the thyroid treatment of hypothyroidism 

 there is no question of their great utility as illustrated by the accompany- 

 ing charts, (See pp. 434 and 440.) Changes of dosage can frequently be 

 both indicated and very accurately controlled in this manner. Whenever 

 possible such methods should be employed. 



In the present, period of overenthusiasm following the recent intro- 

 duction of this method, there seems, however, a tendency to overestimate 

 its value. It is by no means an absolute criterion. Thus several cases of 

 hypothyroidism have been observed by the writer in which thyroid treat- 

 ment promptly brought the metabolic rate to normal, but in spite of this, 

 the patients remained obese, the mental condition was only imperfectly 

 relieved and the temperature remained below the normal. Attempts at 

 further increase of the dosage led to thyrotoxic symptoms with an increase 

 in the metabolic rate. The writer with Henderson has also reported two 

 interesting cases of hypothyroidism in whom complete hysterectomy had 

 been carried out with the result that it was never possible to elevate the 

 metabolic rate to normal by thyroid medication, without a thyrotoxic out- 

 break intervening. The probable explanation for this phenomenon is that 

 the reduction of the basal metabolism in such instances is partly due to the 

 absence of ovarian function, inasmuch as Murlin and Bailey have observed 



