In order to clarify some of the molecular mechanisms involved in the pathogenesis of thyroid proliferating diseases we have investigated the role of TGF-beta in thyroid carcinoma, adenoma and multinodular goiter. TGF-beta 1 expression studies were carried out in surgically removed thyroid tissue isolated from 15 patients affected by multinodular goiter, 4 patients affected by papillary carcinoma and 4 patients affected by follicular adenoma. TGF-beta 1 gene expression, evaluated by Northern analysis, dramatically increased in malignant proliferating thyroid disease and decreased drasticly in multinodular goiter patients with respect to normal thyroid. Immunocytochemical analysis demonstrated that TGF-beta 1 is produced by an autocrine mechanism in the carcinoma and in the benign thyroid disease (multinodular goiter), whereas TGF-beta seems to be produced in adenoma tissues in both an autocrine and a paracrine fashion. This feature further supports the hypothesis that TGF-beta may contribute to regulation of thyrocyte growth and differentiation.

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