Dual effect of transforming growth factor beta on rat thyroid cells: inhibition of thyrotropin-induced proliferation and reduction of thyroid-specific differentiation markers.

Transforming growth factor beta (TGF beta) is now known to have a number of effects other than inducing phenotypic transformation of fibroblastic cells: TGF beta controls proliferation, differentiation, and other functions in many cell types. In this paper we have analyzed the action of TGF beta 1 on a system of differentiated epithelial rat thyroid cells in culture (FRTL5), which depend on the addition of thyrotropin for their growth. TGF beta 1 is able to inhibit the growth of thyroid cells by reducing cell response to thyrotropin. Moreover, in analogy to the effect produced upon other differentiated cells in culture, such as myoblasts and adipocytes, TGF beta 1 modulates the expression of FRTL5-specific thyroid markers, reducing thyroglobulin biosynthesis and the ability to concentrate the iodide.