Detection of autoantibodies against 3,5,3'-triiodothyronine in a hyperthyroid patient (a case report)

A 35-year-old female patient was evaluated for thyroid function and was found to be hyperthyroid clinically and by laboratory tests. During the course of treatment with neomercazole, she developed a bizarre picture with consistently low T3 levels irrespective of her clinical thyroid status and other laboratory tests like serum T4 and TSH levels. The serum of the patient when analysed for the presence of autoantibodies was positive for those against T3. The presence of T3 autoantibodies was confirmed by other laboratory techniques like assessment of blank values in radioimmunoassay, binding of T3-125I to isolated gamma globulin and starch gel electrophoresis. Autoantibodies were found to be present only against T3 and not against. T4 The affinity constant of T3 antibodies was 4 x 10(9) lit. mol-1 as determined by Scatchard plot analysis while total binding capacity was 23 x 10(-11) mol/L.