84 JOHN T. HALSEY 



The Thyroid 



Among all the endoerin products used in therapeutics, no other has 

 up to the present time heen used with such brilliant results or found so 

 wide a field of usefulness as have those made from the thyroid gland. 

 Although Brown-Sequard's employment of testicular extract has the dis- 

 tinction of being the first rational attempt to utilize a product of this type 

 as a therapeutic agent, it was Murray's discovery that thyroid administra,- 

 tion produces such remarkably beneficial effects in myxedema that first 

 demonstrated beyond all doubt the therapeutic value of preparations made 

 from an organ of internal secretion. Notwithstanding that ignorance and 

 credulity have led many physicians and surgeons to make exaggerated and 

 unfounded claims for their therapeutic value, the experience of the three 

 decades that have elapsed since Murray's first report has firmly estab- 

 lished thyroid substance as one of the few absolutely indispensable drugs 

 of our pharmacopeia, with an already wide field of proven usefulness, 

 which in the future may be greatly increased. 



Pharmacology 



Chemistry. The real beginning of our knowledge of the chemistry 

 of the thyroid was Baumann's discovery in 1895 that it contained iodin 

 in organic combination, and the demonstration by him and others that 

 the specific action of the gland and its therapeutic actions were dependent 

 on and exerted only by this iodin containing substance or substances, gen- 

 erally believed to be of proteid nature, until Kendall (e) in 1915 isolated 

 from the thyroid a crystalline substance containing 60 per cent of iodin. 

 This substance named by him thyro-oxy-indol (to emphasize the presence 

 in it of the oxy-imlol nucleus), which is shortened for convenience to 

 thyroxin, has been analyzed and synthetically prepared (Kendall (g) (h), 

 1918) and shown to possess the structural formula: 



I II 



H H O 



H /\ / 



^c c = c-c-c-c 



HI i i \ 



C C C OH H OH 



\/ 



C -N 

 H II 



Further investigations have led Kendall *to the opinion that in the body 

 this structure exists in a different form (the indol ring having opened) 

 with the formula: 



