DISSOCIATION OF THYROTROPIN-DEPENDENT ENZYME-ACTIVITIES, REDUCED IODIDE TRANSPORT, AND PRESERVED IODIDE ORGANIFICATION IN NONFUNCTIONING THYROID ADENOMA AND MULTINODULAR GOITER

Several biochemical and functional modifications demonstrated in goitr ous tissues could reflect the effect of goitrogenic factors. Growth-en hancing agents, including TSH itself, have been involved in goitro-gen esis. To study comparatively the variation patterns of some TSH-depend ent enzymes within single goitrous tissues, we measured the activities of peroxidase (TPO), NADPH-cytochrome-c (cyt-c) reductase, and monoam ine oxidase (MAO) in tissues from cold follicular adenoma and multinod ular goiter. Iodide transport and organification were also evaluated. Perinodular and necropsy tissues were used as controls. The mean TPO a ctivity measured by guaiacol as well as triiodide assays was significa ntly increased in multinodular goiter, whereas a nonsignificant increm ent was observed in cold adenoma. NADPH-cyt-c reductase and MAO were m arkedly increased in the two types of pathological tissues. The indivi dual activities of the three enzymes showed dissimilar modifications w ithin single samples and among different tissues. There was no correla tion in the activities of the enzymes within single specimens from col d adenoma and multinodular goiter, except for MAO and NADPH-cyt-c redu ctase in multinodular goiter, for which a significant correlation was obtained. In this tissue, MAO and TPO measured by guaiacol assay were weakly correlated. TPO activity evaluated by guaiacol oxidation was co rrelated with that measured by triiodide formation in cold adenoma, bu t not in multinodular goiter. The mean iodide organification values as sayed by iodotyrosine formation in the absence of exogenous H2O2 in pa rticulate fractions from cold adenoma and multinodular goiter were wit hin the normal range. A reduced iodide transport, evaluated as the thy roid/medium ratio, was observed in slices from these tissues. The diss ociation of the three enzyme activities in single specimens from cold adenoma and multinodular goiter along with the reduced iodide transpor t in these tissues support the hypothesis that factors other than TSH or with TSH-like effects could be involved in the abnormal thyroid gro wth.