The Effect of Gonadectomy on the Sex-Related Expression of Autoimmune Thyroiditis in Thymectomized and Irradiated Rats


Div of Veterinary Biology, School of Veterinary Studies. Murdoch, Western Australia 6150.


ABSTRACT: Female rats of the PVG/c strain were found to be approximately four times more susceptible than males to the induction of autoimmune thyroiditis by thymectomy and irradiation (Tx-X) (female vs male incidence, 60%:14%). Similarly, the severity of the lesion was generally greater in females than males. Female Tx-X rats also had a significantly higher incidence of antibodies to thyro-globulin than males (incidence, 67%:24%, respectively) and developed higher titers.

Prepubertal orchiectomy had a profound influence on both the severity and incidence of thyroiditis. Orchiectomized Tx-X males were found to have changes approximating those of Tx-X females (72%:60%, respectively). A corresponding influence was also noted on the incidence and titer of antibodies to thyroglobulin (incidence, 78%:67%, respectively). Postpubertal orchiectomy similarly intensified the incidence and severity of the disease.

Ovariectomy also caused a slight but significant increase in autoimmune thyroiditis as compared to entire Tx-X females (78%:60%, respectively).

Sham-gonadectomized control rats did not differ in overall susceptibility from entire Tx-X rats.

These observations indicate that the incidence and extent of autoimmunity induced in this particular model are modulated by sex steroid hormone production rather than by sex-linked gene(s) directly determining susceptibility. It is also apparent that this influence is not exerted through the thymus gland.