There was a relative increace in the amount of c:- culating 1317_jod4 e in e in roportion to other iodinated compounds shortly after the break in the c tivity in umerous instances. A coincident rise observed in the excretion of radi he urine seemed to weflect a failure of retrapping of iodide by the gland. It had been the policy to prepare butanol extracts of serum from whi £ the quantitative chromatograms were made. Concentrating the icdinated nhaneces the possibility of detecting more unusual substances that might nly in minute quantities in whole serum. The butanol used for extractio aturated with water so that iodide in addition to iodinated organic mole ecovered. Other chromatograms were prepared on whole serum for purposes he extractability of the radioactivity in the serum using this extractio bserved to decline as the radiation effect took place in the thyroid. A ime chromatograms from whole serum showed that the radioactivity represe nsoluble fraction and remaining at the application point increased marke epresented cicculating thyroglobulin. In som instances the extractabili ormally is 85% to 95%, dropped as low as 65% to 70%. Where this occurre ubsequent clinical improvement was usually quite prompt and hypothyroidi redictable outcome. he Significance of Mono- and Diiodotyrosine in the Circulation Following or Hyperthyroidism some ompounds present was es was f comparison. system was the same ing the y. This > which the was a 31y Therapy Farran, Lea, Goolden and Abbatt had reported that the presence of m ho~ and Jodggyrosine in the circulation in patients with thyrotoxicosis was an i hdication therapy might fail. Their observations had been made on single ‘lood from 92patients. In contrast to their observations, when miltiple n the form of serial quantitative chromatograms were available on appro _ atients with thyrotoxicosis treated with 1311, the observations of the ‘ere not confirmed. n the circulation ultimately displayed a more striking radiation effect. atients the mono- and diiodotyrosine began to appear on the fourth or fi ollowing the administration of 1811. This appearance was usually accam adioactivity remaining at the application point when whole serum was . prompt subsequent clinical improvement, and a high probability of subse ‘ypothyroidism. See attached Figure 7. It was concluded that the presencp “issue. wornt of L3lz When found, it was usually in minor quantities in the circulation ‘comparison of Two or More Treatment Doses in the Same Individual We have been on the look cut for patients who required further re adioactive iodine so that it would be possible to compare all of the obs iituations may exist in the patient who requires further treatment. Some ittle clinical radiation effect; others may have had an effect which was fonsiderable //