Autoimmune hepatitis and hypothyroidism associated with anti-thyroid hormone autoantibodies

A 40-year-old hypothyroid female who had been treated with synthetic thyroxine was admitted to our hospital in October 1988 due to abnormal liver function tests. She had low serum free triiodothyronine (T3; 2.3 pg/ml) and high serum thyrotropin (TSH; 20.8 microU/ml) concentrations. On the other hand, the serum free thyroxine (FT4) level was inappropriately high, being 2.46 ng/dl. Immune precipitation of radiolabeled thyroid hormones with her serum disclosed the binding of 125I-T3 and 125I-T4 to the extent of 9.5% and 11.3%, respectively (normal ranges for 125I-T3 and 125I-T4 binding are less than 6.3% and 5.9%, respectively). 125I-T4 binding to the patient's serum gamma globulin was completely displaced with the addition of unlabeled T4. Further examination disclosed that anti-T4 antibodies in her serum belong to IgG kappa class immunoglobulin.