TRANSFORMING GROWTH-FACTOR-BETA-1 IS MORE EXPRESSED IN THYROID FOLLICULAR ADENOMA THAN IN NORMAL TISSUE

It is well known that TSH is the main factor responsible for thyrocyte proliferation and growth. Recent studies have shown that other growth factors, including transforming growth factor-beta 1 (TGF-beta 1), ha ve an important role in the control of thyrocyte proliferation and dif ferentiation. The aim of the study was to evaluate the expression of t he TGF-beta 1 gene in thyroid follicular adenoma (FA) by Northern anal ysis, and its protein localization by immunohistochemistry. Surgically removed thyroid tissue from 56 patients with thyroid FA was screened for the study. Normal thyroid tissue from 4 patients with papillary ca rcinoma was used as a control. Sixteen FA (8 with a ''cold'' and 8 wit h a ''hot'' scintiscan pattern) having homogeneous histological charac teristics were subsequently selected. FA showed greater TGF-beta 1 gen e expression than control tissue. There was not a statistically signif icant difference between ''cold'' and ''hot'' FA. Immunohistochemistry analysis showed that TGF-beta 1 was located in various histological s tructures of the adenomas (thyrocytes, endothelium, perinervium and co nnective tissue); on the other hand, perinodular and control tissue di d not show appreciable TGF-beta 1 protein. Our data suggest that TGF-b eta 1 may be involved in the pathogenesis of FA. The different TGF-bet a 1 distribution in thyrocytes, endothelium, perinervium and connectiv e tissue in FA suggests that TGF-beta 1 may be variably expressed duri ng the natural history of FA. Since no significant difference in TGF-b eta 1 gene expression between ''hot'' and ''cold'' adenomas was found, it appears that other factors are involved in their functional differ entiation.