

THE BIOCHEMISTEY OF THE THYROID GLAND 263 



growth in young white rats fed a hog-thyroid preparation containing 0.34 

 per cent of iodin is definitely greater than in rats of the same litter fed 

 a sheep-thyroid preparation containing 0.18 per cent of iodin, and have 

 obtained some evidence that the degree of hypertrophy of heart, liver, kid- 

 neys, etc., which results from such feeding is proportional to the iodin con- 

 tent of the thyroid fed. 



Assuming that thyroxin is the essential constituent of the secretion, and 

 results from the passage of thyroid through the alimentary tract, since 

 Kendall has shown that in thyroid it bears a definite relation to the total 

 iodin content, it follows that thyroid activity must be directly proportional 

 to iodin content. 



The Chemistry of the Pathological Thyroid Gland 



Few comparative observations have been made on the chemical com- 

 position of the normal and pathological gland, with the exception of those 

 connected with iodin. Cholesterol was, according to Bubnow, found in a 

 struma-cyst by Scherer (1843) and by Kletzinsky (1852). Eeinbach 

 claimed to obtain a specific sugar from a colloid goiter ; the melting point 

 of the osazon was 193 C. Goitrous glands contain relatively more silica 

 than normal (0.043 Si as compared with 0.017, Schulz). From an analy- 

 sis of Morgenstern's figures it was found that goitrous glands contain mag- 

 nesium, apparently an abnormal constituent, and their calcium, phos- 

 phorus, and chlorin figures are possibly slightly higher than normal. 



Baumann (1895) noted that goitrous glands contain proportionately 

 less iodin, but Oswald (a) (1897) showed that the total amount in such 

 glands is not below normal. Hunziker considers that goiter amounts to a 

 fundamental hypertrophy of the thyroid caused by the effort of the organ- 

 ism to make up for a deficient iodin supply ; with this may be connected 

 Seidell and Fenger's observations on cattle thyroid enlargement in cold 

 weather and the apparently inverse ratio which exists between iodin per- 

 centage and size of thyroid even with normal glands of the same species. 

 Marine and his co-workers have devoted much attention to the amount of 

 iodin present in pathological glands. Marine and Lenhart find that the 

 iodin content varies inversely with the degree of hyperplasia. The rapidity 

 with which iodin is taken up by the gland depends on the degree of active 

 hyperplasia. Exopthalmic goiter is constantly accompanied during the 

 progressive stages by thyroid hyperplasia, the iodin content varying in- 

 versely with the degree of hyperplasia. In endemic cretinism and myxe- 

 dema there is a very low iodin content. 



Pellegrini (a) (1915) states that the amount of iodin does not depend 

 on the state of nutrition. There is an increase above the average in cases 

 of sudden death, cirrhosis of the liver, and acute inflammatory processes 



