THE THYEOID 27 



Endemic goiter. Before dismissing the subject 

 of hyposecretion a word must be said about the 

 cases known as endemic goiter. In such cases the 

 front part of the neck becomes swollen, due to the 

 enlargement of the thyroid gland (hence the name 



edge of chemistry must be assumed at this point, I would suggest 

 that those readers who do not possess such knowledge had 

 better skip this footnote. 



The first detailed account of the isolation of the active prin- 

 ciple appeared in 1919, when Kendall published his paper, "On 

 the Isolation of the Iodine Compound Which Occurs in the 

 Thyroid," in the Journal of Biological Chemistry. The research 

 was begun in 1910, so that no less than nine years of continuous 

 work were spent in attempts to isolate the hormone. Up to 1919, 

 33 grams (a little over an ounce) of the hormone "thyroxin" had 

 been isolated from 6.550 pounds of fresh thyroid. 



Kendall's method of isolating thyroxin is as follows: Fresh 

 thyroid gland is hydrolized with sodium hydroxide. The fats 

 are removed by rendering the sodium soaps insoluble, and the 

 clear alkaline filtrate is acidified. Acid soluble and acid insoluble 

 portions are obtained, each containing one-half of the total 

 iodine. (Kendall has confined his attention to the acid-insoluble 

 portion, which contains all the thyroxin, but what type of 

 iodine compound is in the acid soluble portion, and to what 

 extent that iodine combination is of importance, remains to be 

 seen.) The acid insoluble portion is filtered off, the precipitate 

 redissolved in sodium hydroxide and reprecipitated with hydro- 

 chloric acid. The substance is next air-dried and dissolved in 95 

 per cent, alcohol. A hot, concentrated, aqueous solution of barium 

 hydroxide is added to the alcoholic filtrate, and the mixture 

 heated under a reflux condenser. This is next filtered, a small 

 amount of sodium hydroxide added to the filtrate, and carbon 

 dioxide passed through the solution. Barium and sodium car- 

 bonates are removed by filtration, and the alcohol is removed by 

 distillation. 



The product is purified by redissolving in alcoholic sodium 

 hydroxide and again passing in carbon dioxide. The sodium car- 

 bonate is filtered, and the alcohol evaporated. The last traces of 

 alcohol are removed by heating on a water bath. At this point 

 the monosodium salt of thyroxin separates. The thyroxin itself 

 is obtained by dissolving the salt in alcoholic alkali, and pre- 

 cipitating with acetic acid. 



