Thyroid functional status and TSH receptors of cold nodular tissue

TSH receptors of plasma membrane fractions of human cold thyroid adenoma and perinodular thyroid tissues (PTT), assumed by pathohistological analysis to be normal, were examined. In perinodular thyroid tissues (PTT) obtained by partial thyroidectomy from twelve euthyroid female patients 125I-TSH binding (as determined by equilibrium binding analysis on particulate plasma membrane preparations) was found to be significantly increased as compared with scintigraphically cold thyroid nodular tissues (CTN). In all examined thyroid tissues Scatchard analysis of TSH binding revealed two kinds of binding sites: these with high affinity showed a significantly increased dissociation constant (Kd1), while these with low affinity showed a decreased dissociation constant (Kd2) in PTT as compared with CTN. The capacity of low affinity binding sites in PTT was found to be decreased in comparison with CTN tissues. These results suggest that the changes in affinity of TSH receptors sites as well as iodine deficiency of thyroid tissues may be an important events in functional status of analysed perinodular and cold nodular thyroid tissues.