Immunocytochemical localization of estrogen and progesterone receptors in human thyroid

The presence of steroid hormone receptors has previously been suggested in thyroid tissue by biochemical means. Our studies were designed to confirm these results and to localize the specific receptor-containing cell type using a novel immunocytochemical method. Monoclonal antibodies specific to estrogen receptors (ER) and progesterone receptors (PgR) were used to localize these steroid hormone receptors in the human thyroid gland. Frozen tissue sections from surgical specimens excised from 22 patients of both sexes with benign thyroid disease were studied. The sections were incubated with rat antiestrophilin and antiprogesterone receptor antibodies and were then exposed to rabbit anti-rat IgG and to rat peroxidase-antiperoxidase complex. The reaction product was visualized with diaminobenzidine tetrahydrochloride and hydrogen peroxide. Four specimens were positive for both ER and PgR, 16 were ER-positive and PgR-negative, and two were negative for both ER and PgR. Positive reactivity was limited to the follicular lining cell nuclei and varied from focal to diffuse. The immunohistochemical findings confirmed the presence of ER and PgR in the thyroid tissue and demonstrated for the first time that these receptors are present only in the nuclei of the lining cells of the thyroid follicle. The role of steroid hormone receptors in the thyroid in health and disease remains to be explained.