RT Journal T1 RElation of iodine to the thyroid gland JF Journal of the American Medical Association JO Journal of the American Medical Association YR 1929 FD September 21 VO 93 IS 12 SP 922 OP 922 DO 10.1001/jama.1929.02710120034011 UL http://dx.doi.org/10.1001/jama.1929.02710120034011 AB Few chapters in the history of biochemical discovery are of greater practical as well as scientific interest to physicians than that which involves the relations of iodine to the thyroid gland. Shortly after the finding of the element in the thyroid, in 1895, Baumann and his co-workers in Freiburg attempted to isolate the "active principle" that contained the newly discovered component. By hydrolysis a potent substance containing as much as 9 per cent of iodine was separated and introduced into therapy under the designation of iodothyrin. Today this is recognized to be a mixture of compounds. More than twenty years later, Kendall succeeded in isolating a crystalline substance, thyroxin, containing 65 per cent of iodine and apparently possessing the characteristic therapeutic potencies of thyroid substance. Kendall originally believed that thyroxin was a derivative of the amino-acid tryptophan, containing the indole nucleus in partly oxidized form. It remained for Harington, in