INSULIN-LIKE GROWTH-FACTOR-I IN HUMAN THYROID-TISSUE - SPECIFIC LOCALIZATION BY IMMUNOHISTOCHEMISTRY AND IN-SITU HYBRIDIZATION

Insulin-like growth factor I and II (IGF-I and IGF-II) have been impli cated in the replication of normal thyroid follicular cells in vitro. This study evaluates the distribution and abundance of immunoreactive IGF-I by histochemical analysis in human thyroid tissue with different histopathologic characteristics. We used two types of highly specific and sensitive polyclonal rabbit anti-IGF-l antibodies and one monoclo nal antibody (MAb) with the immunoperoxidase technique on sections of 25 glands harboring adenomatous goiter; 11 glands with follicular aden oma (FA); 45 glands with thyroid carcinoma of papillary, follicular, a nd undifferentiated types; and 18 glands with Graves' disease. Immunor eactive IGF-I was present in some thyroid follicular cells of all thyr oid tissues examined. The percentage of cells staining positively vari es among the different processes, being lowest in normal thyroid tissu es and highest in all thyroid carcinomas. The cytoplasmic pattern of I GF-I immunoreactivity also varied among the different thyroid conditio ns. Furthermore, using nonradioactive in situ hybridization (ISH) we d etected IGF-I mRNA in the thyroid cells of adenomatous goiter. The exp ression was higher in the histologically hyperplastic areas. These fin dings provide further support for an autocrine and/or paracrine role o f IGF-l in the function and/or growth of normal thyroid follicular cel ls and suggest that IGF-I may play a role in the dysfunctional growth of thyroid follicular cells in adenomatous goiter, thyroid carcinoma, and Graves' hyperthyroidism.