INSULIN-LIKE GROWTH-FACTOR-I AND INSULIN-LIKE-GROWTH-FACTOR RECEPTOR IN THYROID TISSUES OF PATIENTS WITH GRAVES-DISEASE

Growth factors are frequently involved in the regulation of mitosis an d differentiation of several cell types and insulin-like growth factor -1 (IGF-I) is actively involved in the thyroid stimulating hormone-med iated proliferation of thyrocytes. In view of the pivotal role of IGF- 1 in thyrocyte proliferation and of the still unsettled role of this g rowth factor in the pathogenesis of hyperplastic thyroid lesions, we i nvestigated the expression of IGF-I and of its corresponding receptor, by means of immunohistochemistry, in the surgical specimens obtained from six patients with Graves' disease. Moreover, IGF-1 mRNA expressio n was analysed in one such case by means of Northern hybridisation. Al l samples showed consistent intracytoplasmic immunoreactivity for both IGF-1 and IGF-I receptor; the vast majority of hyperplastic thyrocyte s were strongly decorated by the two antibodies used in this study whe reas stromal cells displayed IGF-1 immunoreactivity only. IGF-1 mRNA w as markedly overexpressed in Graves' disease in comparison with normal thyroid tissues. The results of this study suggest that IGF-1 and IGF -1 receptor may be actively involved in the pathogenesis of Graves' di sease; furthermore, IGF-1 and IGF-I receptor apparently act by differe nt mechanisms (paracrine vs. autocrine) as suggested by their differen tial expression in epithelial and stromal cells.