CORRELATION OF ORBITAL MUSCLE CHANGES EVALUATED BY MAGNETIC-RESONANCE-IMAGING AND THYROID-STIMULATING ANTIBODY IN PATIENTS WITH GRAVES OPHTHALMOPATHY

To evaluate the relationship between eye changes and autoantibody to t he thyrotropin receptor in patients with Graves' disease, we evaluated the eye changes using magnetic resonance imaging and the results were correlated with thyroid-stimulating antibody, thyrotropin binding inh ibitor immunoglobulin and thyroid growth activity. Subjects were 15 pa tients with Graves' disease who had Graves' ophthalmopathy, including exophthalmos and other signs and symptoms, and nine patients without o phthalmopathy; all were maintained in a euthyroid state by antithyroid drugs. The thyrotropin-binding inhibitor immunoglobulin was measured by a kit, and thyroid-stimulating antibody and thyroid growth activity were evaluated by cyclic adenosine 3', 5'-monophosphate production an d [H-3]thymidine incorporation, respectively, by cultured functional r at thyroid lined cells. The sum of the swelling ratios (muscle thickne ss to the diameter of the optic nerve) of the four extraocular muscles correlated well with the degree of exophthalmos. The thyrotropin-bind ing inhibitor immunoglobulin was positive in nine out of 15 patients w ith ophthalmopathy; however, no correlation was observed between the a ctivity and exophthalmos or muscle swelling. No significant correlatio n was observed between muscle changes and thyroid growth activity eith er. On the other hand, thyroid-stimulating antibody (642 +/- 91%) in G raves' patients with ophthalmopathy was significantly (p < 0.02) highe r than that (315 +/- 84%) in patients without ophthalmopathy. Moreover . the level of the stimulating activity in Graves' patients with ophth almopathy showed a significant (p < 0.02) positive correlation with th e sum of the swelling ratios of the individual eight eye muscles. Thes e results suggest that thyroid-stimulating antibody has a close relati on to Graves' ophthalmopathy.