Clinical significance of autoimmune thyroid disease in myasthenia gravis.
We investigated thyroid function and autoimmunity in 74 (61% females) consecutive patients with MG. 30 of these patients were tested twice: the time between the investigations ranging from 1 to 4 years. MG was diagnosed on the basis of typical clinical symptoms, a positive tensilone-test, and/or detectable acetylcholine antibodies and/or repetetive stimulation tests. Eye involvement was present in 86%, concurrent thymomas in 56%. The following parameters were measured in the serum of these patients by commercially available kits: free and total T4, TSH, TSH-Receptor-Antibodies ("TRAB"), antibodies against thyroglobulin (Tg-Ab), against thyroid microsomes (M-Ab) and against acetyl-choline-receptors . An age matched group of 50 patients (54% females) with no known thyroid disease from a cardiological ward and from the neurological outpatient department served as control. There was only 1 MG patient with overt thyroid dysfunction (iodine induced thyrotoxicosis in a patient with autonomous adenoma and no circulating thyroid autoantibodies detected at the second investigation). There were, moreover, 1 euthyroid MG-patient on L-thyroxine therapy with a history of Hashimoto's disease and positive thyroid autoantibodies and 1 other MG-patient with mildly elevated TSH without elevated thyroid antibodies, who has had subtotal thyroidectomy without substitution therapy years before for unknown reasons. Tg-Ab were positive (>360 IU/ml) in 5%, M-Ab were positive (>154 IU/ml) in 15% of the MG patients. The control group had 4% Tg-Ab and 6% M-Ab. TRAB levels were normal in all patients and controls. The relative increase in M-Ab frequency was not statistically significant (x-square test). We conclude from our results, that autoimmune thyroid disease may be associated with MG but that the occurrence of thyroid dysfunction induced by autoimmunity is a very rare phenomenon in MG.
Weissel
M
M
Clinic for Internal Medicine III and Ludwig Boltzmann Institute for Nuclear Medicine, University of Vienna, Austria. Michael.Weissel@akh-wien.ac.at
Mayr
N
N
Zeitlhofer
J
J
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000906:Antibodies / Q000097:blood; D001323:Autoantibodies / Q000097:blood; D001327:Autoimmune Diseases / Q000150:complications*; D005260:Female; D006801:Humans; D018828:Immunoglobulins, Thyroid-Stimulating; D008297:Male; D008875:Middle Aged; D009157:Myasthenia Gravis / Q000097:blood / Q000150:complications* / Q000276:immunology; D011950:Receptors, Cholinergic / Q000276:immunology; D011989:Receptors, Thyrotropin / Q000097:blood; D013954:Thyroglobulin / Q000276:immunology; D013959:Thyroid Diseases / Q000097:blood / Q000175:diagnosis / Q000276:immunology*; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood
D000906:Antibodies; D001323:Autoantibodies; D018828:Immunoglobulins, Thyroid-Stimulating; D011950:Receptors, Cholinergic; D011989:Receptors, Thyrotropin; C056626:thyroid microsomal antibodies; C094372:thyrotropin-binding inhibitory immunoglobulin; D013972:Thyrotropin; D013954:Thyroglobulin; D013974:Thyroxine