Lymphocytic thyroiditis in free-ranging wolverines from Alaska, USA

We report on thyroid gland lesions in 47 free-ranging wolverines (Gulo gulo). The lesions were observed from 2014-2022 and originated from 2 distinct genetic clusters, northern Alaska (NA) and central Alaska (CA). Lymphocytic thyroiditis (LT) was observed in 11 of 25 of the NA cluster and 2 of 22 of the CA cluster. Thyroid gland interstitial fibrosis, infiltration by lymphocytes, follicular disruption, and follicular atrophy were observed in 8 of 22 CA cluster wolverines. Thyroid gland lymphocytes uniformly labeled with CD3, consistent with T lymphocytes. The relative risk for LT was 4.8 times higher in the NA population than in the CA population. Testicular inactivity was observed in 8 of 8 male NA wolverines with LT and in 3 of 7 NA wolverines without LT. Testicular inactivity was observed in only 1 CA wolverine. Thyroid function blood testing was not available for any of our cases. Further exploration to identify the significance of LT, factor(s) contributing to the development of LT, and the higher prevalence of LT in the NA cluster would be important considering the socio-ecologic significance of wolverines within Arctic and subarctic ecosystems and to indigenous peoples.