59-4 CHEMICAL PATHOLOGY OF THE DUCTLESS GLAXDS 



ill animals, curative effect on myxedematous patients), whereas the 

 nucleoprotein is witliout these effects. Analysis of the thyreoglobulin 

 from various animals has shown it to be of quite constant quantitative 

 composition except for the iodin, which may vary greatly in amount. 

 Normal human thyreoglobulin (from persons living in non-goitrous 

 districts) had the following percentage composition: 



C = 51. So, H = 0.88, X = 15.49, I = 0.34, S = l.SG. 



Th,yreoglobulin from goitrous districts contains much less iodin 

 (0.18-0.19 per cent.l, and from calves born with goiters a thyreo- 

 globulin was obtained that agreed in all respects with nonnal thyreo- 

 globulin, except that it contained no iodin at all. On the other hand, 

 administration of iodides to patients causes the thyreoglobulin to 

 become rich in organically bound iodin.^** From these facts Oswald 

 believes that the thyreoglobulin, as first secreted by the glandular epi- 

 thelium, is free from iodin, and that it combines later with iodin from 

 the circulating blood. As yet it has not been ascertained how the 

 iodin is bound to the protein. It is well known that large amounts 

 of iodin can be introduced into the protein molecule, apparently 

 through its substitution for hydrogen in the aromatic radicals (tyro- 

 sine, phenylalanine, etc.) Thyreoglobulin is not, however, simply an 

 iodized protein, for the iodized proteins that can be artificially pre- 

 pared do not possess the physiological activity of the thyreoglobulin ; 

 furthermore, the saturated iodized proteins contain generally from 5 

 to 12 per cent, of iodin, as contrasted with the 0.8 to 0.8 per cent, of 

 thyreoglobulin. Oswald has shown that in thyreoglobulin the iodin 

 is not bound to tyrosine, since this can be removed by tryptic digestion 

 without decreasing the amount of iodin in the rest of the molecule ; 

 possibly the iodin is bound to phenylalanine.-" F. C. Koch -^ finds that 

 the full activity of the gland is contained in the thyreoglobulin, and 

 also in the metaprotein fraction of this globulin, while simpler cleav- 

 age products show less and less activity per unit of iodin content. 

 Tie could find no thyroid activity in iodin compounds of histidine, and 

 di-iodotyrosine was found inactive by Strouse and Voegtlin.-- 



The remarkable influence of the thyroid on the development of tad- 

 poles (Gudernatsch *) is exhibited by the thyreoglobulin, but not by 

 any other iodin compound that has been tried, except possibly by 

 iodized blood protein (Morse ^^''). Abderhalden,^-"' however, found 

 lliat if th^-roid was digested until nearly or (piite biuret-free and then 



10 Nape! and Tfoos (Arch. f. Anat. u. Physiol., 1002, p. 2(17) foiiiul t'lat ad- 

 ministration of bromidos had no effoct upon the amount of iodin in tlu> thyroid, 

 and no storaf^o of bromin ta'^o* T-'aoe. Administration of pilocarpine docs not. 

 increase ilie amount of iodin iTi tlic thyroid. 



20 Niirn1)cri:. llofincisicr's Bcitr.. 1007 (10), 125. 



•■;i Jour. l?iol. Cliem., 101:5 (14), 101. 



-'-•Jour. Pliarni. and F\p. Ther., 1010 (1). 123. 



1!'^' Jour. l?iol. C'hcm., 1015 (10), 421. 



i'"'Arcli. ^'cs. Phvs.. 1015 (102), 00. 



