Beneficial effect of testosterone in the treatment of chronic autoimmune thyroiditis in rats

Early thymectomy and sublethal irradiation of normal rats consistently induces a sex-dependent chronic autoimmune thyroiditis. Females are much more susceptible to this autoimmune disorder than are males. The possible therapeutic effects of testosterone (Te) on established autoimmune thyroiditis has been investigated in this model. The pathologic condition of the gland before treatment was monitored by a thyroid grafting and extirpation techniques. Te administration by either parenteral injection or implantation caused significant regression of established thyroiditis. Repeated doses of Te ester in oil were found to be more effective than powdered free-Te given by implantation, and frequently produced complete resolution of chronic lesions involving the entire gland. In these thyroids, there was reappearance of normal thyroid architecture and complete absence of mononuclear cellular infiltration. However, no inhibitory effect on serum autoantibody production to thyroglobulin was noted with any form of Te treatment. These observations strengthen the concept that cellular rather than humoral mechanisms are involved in the pathogenesis of thyroiditis.