HYPOTHYKOimSM 421 



The diagnosis of hypothyroidism should never depend on laboratory 

 tests alone nor, as can now be stated, solely upon the clinical symptoms. 

 Perhaps, however, too great reliance is being placed nowadays en the basal 

 metabolic determinations, the present enthusiasm suggesting that of the 

 period of the introduction of the Wassermann test. If hypothyroidism be 

 present, it will always betray itself to the careful observer by some small 

 clinical signs as indicated in the text. The basal metabolic rate should, 

 however, certainly be estimated whenever possible. If, then, in an obscure 

 case we find some trifling clinical suggestions of hypothyroidism and the 

 laboratory reports a depressed basal metabolism, an abnormal blood glu- 

 cose curve, lymphocytosis, mononucleosis, retardation of growth of the 

 bone nuclei by rontgen-ray, we can frequently establish the diagnosis. 



Much could be written in regard to the therapeutic test which repre- 

 sents the court of last resort in attacking the problem of diagnosis of 

 obscure types of hypothyroidism. As usually employed, the therapeutic 

 test is of only very moderate value. In carrying out this procedure it is 

 not sufficient to give a suspected case a large dose of thyroid for a few 

 days trial. On the contrary, it is frequently necessary to painstakingly 

 study the effect of weeks of small but increasing dosage on the clinical 

 symptoms and metabolic rate before hypothyroidism can be safely excluded 

 or determined to be present. It is well to bear in mind that the required 

 amount of thyroid hormone is an exact quantity which can only be dis- 

 covered by continued study and observation. ~No definite rules as to 

 dosage in the therapeutic test can be given. It is the writer's custom to 

 begin with a, % gr. of standardized thyroid extract or 0.2 mg. thyroxin 

 daily, estimating the basal metabolism at fortnightly intervals. A rise of 

 the rate to normal accompanied by clinical improvement is a strong evi- 

 dence for hypothyroidism. Large doses of thyroid will elevate, through 

 toxic effect, the basal metabolism in conditions other than hypothyroidism ; 

 so caution must be observed. 



Differential Diagnosis 



Differential Diagnosis in Children. In the case of infants and young 

 children, errors of diagnosis remain unfortunately rather common, espe- 

 cially as the laboratory aids to diagnosis cannot be carried out or are less 

 reliable. The differential diagnosis of light or incipient cases requires at 

 times a high display of diagnostic acumen. Bearing in mind the enormous 

 importance of an early diagnosis for the future of the individual, every 

 effort should be made to avoid error. 



In the presence of a growth anomaly, if the symptoms and signs are 

 chiefly referable to a single organ complex, the case is probably not one 

 of hypothyroidism. Thus a predominance of central and peripheral mor- 



