The effect of thyroxine on spontaneous thyroiditis in BB/W rats.

The effect of T4 on the incidence of lymphocytic thyroiditis and on titers of antibodies to thyroglobulin and thyroid microsomal antigen was studied in BB/W rats that are prone to develop spontaneously autoimmune thyroiditis and diabetes. Thirty-three animals were separated in two groups. Rats in one group had 1 mg T4 per liter of drinking water, and the other group was given no T4. After 3-4 months of therapy the T4-treated group had a reduced production of antibody to thyroglobulin (p less than 0.05) and to microsomal antigen (p less than 0.005) and a significantly lower frequency of lymphocytic thyroiditis (p less than 0.05). Our data are consistent with previous findings in experimentally induced thyroiditis in rats and suggest that T4 has an immunosuppressive effect.