Iodoamino acids in abnormal and grossly normal thyroids: Comparison between 125I and 127I distribution

Patients with thyroid cyst (TC), non-toxic nodular goiter (NNG), follicular adenoma (FA) and papillary carcinoma (PC) were given a tracer dose of 125I 40h prior to surgery. Tissue specimens were hydrolysed with Pronase and their labeled iodocompound distribution determined by paper or thin layer chromatography; they were then derivatized and their stable iodoamino acids (IAA) determined by gas liquid chromatography (GLC). Specific activity (SA) of MIT, DIT and T4 was within the same range in TC, FA and grossly normal part of a PC, and was markedly lower in two NNG. SA of T3 was very high in a TC, and higher than that of other IAA, in one NNG, indicating preferential synthesis. SA of MIT and DIT was very high in grossly normal part of a second PC but stable iodothyronines were undetectable. Specimen therefore was biochemically abnormal though grossly normal. In the two abnormal specimens of PC stable IAA were undetectable, even though type of distribution of labeled IAA in one specimen closely approximated that found in TC, FA and NNG. In a second abnormal PC specimen RAI uptake was too low for analysis to be carried out. By combining labeled and stable IAA measurements new parameters for studying human thyroids have been obtained.