Abstract
Autoantibodies against thyroid hormones were experimentally induced and clinically
observed. Rats were immunized with a single dose of T3-conjugate, T4-conjugate or both. Six months later total T3 and total T4 were measured by radioimmunoassays after alcohol extraction as well as TSH in rats
(rTHS). Also antibody titers against T3 and T4 were determined. Oxygen consumption of immunized and control rats was measured in
special metabolic cages. After immunization T3 and/or T4 concentrations were markedly elevated in close correlation to the respective antibody
titers. rTSH was not changed. Oxygen consumption was not altered in immunized animals,
whereas thiamazol treated rats showed diminished oxygen consumption indicating decreased
basal metabolic rate. Clinically occurring thyroid hormone autoantibodies can be detected
by RIA using charcoal separation for bound and free hormone since they result in high
unspecific binding. Such sera are subjected to antibody titer determination and total
T3 and T4 are measured after alcohol extraction. T3 autoantibodies were observed in euthyroid and hyperthyroid sera, and their titers
were again correlated to total T3 concentrations. It can be concluded, that the increased total hormone concentrations
in antibody positive sera are biologically irrelevant, since rTSH and oxygen consumption
were normal suggesting normal free hormone concentrations. In patients with thyroid
hormone autoantibodies the diagnosis cannot be made from total hormone concentrations
or antibody titers, but must be made on the basis of clinical appearance and TRH tests.
Key words
Thyroid Hormone Autoantibodies - Total T3
- Total T4
- Active Immunization - Oxygen Consumption
