Several biochemical and functional modifications demonstrated in goitrous tissues could reflect the effect of goitrogenic factors. Growth-enhancing agents, including TSH itself, have been involved in goitrogenesis. To study comparatively the variation patterns of some TSH-dependent
enzymes within single goitrous tissues, we measured the activities of
peroxidase (TPO),
NADPH-
cytochrome-c (cyt-c)
reductase, and
monoamine oxidase (
MAO) in tissues from cold
follicular adenoma and multinodular
goiter.
Iodide transport and organification were also evaluated. Perinodular and necropsy tissues were used as controls. The mean TPO activity measured by
guaiacol as well as triiodide assays was significantly increased in multinodular
goiter, whereas a nonsignificant increment was observed in cold
adenoma.
NADPH-cyt-c
reductase and
MAO were markedly increased in the two types of pathological tissues. The individual activities of the three
enzymes showed dissimilar modifications within single samples and among different tissues. There was no correlation in the activities of the
enzymes within single specimens from cold
adenoma and multinodular
goiter, except for
MAO and
NADPH-cyt-c
reductase 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 correlated with that measured by triiodide formation in cold
adenoma, but not in multinodular
goiter. The mean
iodide organification values assayed by
iodotyrosine formation in the absence of exogenous H2O2 in particulate fractions from cold
adenoma and multinodular
goiter were within the normal range. A reduced
iodide transport, evaluated as the thyroid/medium ratio, was observed in slices from these tissues. The dissociation of the three
enzyme activities in single specimens from cold
adenoma and multinodular
goiter along with the reduced
iodide transport in these tissues support the hypothesis that factors other than TSH or with TSH-like effects could be involved in the abnormal thyroid growth.