EVIDENCE FOR THYROID-GROWTH-STIMULATING IMMUNOGLOBULINS IN SOME GOITROUS THYROID DISEASES

Abstract

To investigate the possibility that goitrous enlargement in autoimmune thyroid disease could be induced by autoantibodies stimulating thyroid-cell growth, organ cultures of guineapig thyroid segments were exposed to immunoglobulins (Ig) from several groups of patients with goitrous and non-goitrous thyroid diseases. The growth-stimulating effects of the immunoglobulins were measured with nucleic-acid cytophotometry and confirmed with thymidine autoradiography. DNA synthesis was enhanced by immunoglobulins from patients with goitrous Graves' disease, whereas normal immunoglobulins caused some inhibition. Immunoglobulin from non-goitrous thyrotoxic patients and from patients with primary myxœdema gave responses comparable to the normal Ig. Thyroid growth was also induced by Ig from patients with Hashimoto goitres, especially those with recurrences after partial thyroidectomy or those in whom the gland failed to shrink on full thyroxine replacement. Ig from 10 women with "simple" euthyroid colloid goitres, 3 of whom had had one or more recurrences after previous thyroidectomies, also gave rise to increased DNA synthesis in the thyroid cultures, whereas Ig from goitres of known ætiology, such as single autonomously functioning adenoma, or dyshormonogenesis failed to stimulate cell growth under the same conditions. In the thyrotoxic patients the trophic effects in vitro correlated well with the size of the glands in vivo rather than with the degree of toxicity. These results suggest the existence of distinct types of "thyroid-stimulating" antibodies, some of which increase hormone release, whereas others promote thyroid-cell growth. They also suggest that some forms of euthyroid goitres, histologically classified as colloid goitres, may be due to thyroid growth-stimulating antibodies and may be considered as a new form of thyroid autoimmunity.