A Postmortem Finding of a Colloid Goiter in an American Black Bear (Ursus Americanus)

The present case report aims to describe a postmortem finding of a colloid goiter, without obvious clinical signs of endocrine disease in a 30-year-old American black bear (Ursus americanus) from the “Zoo” in the city of Sofia, Bulgaria. A clinical examination due to a bad general condition was performed under anesthesia and a computed tomography was conducted. After the established irreversible spondylarthrosis changes the bear was euthanized. Postmortem, the thyroid gland was pathologically examined and typical findings for a colloid goiter were observed. Hibernating mammals such as the American black bear have been shown to enter a state of physiological hypothyroidism during hibernation. Hormonal signals from the thyroid gland have been suggested to be a key mediator of hibernation. From the presented case could be assumed that the captive life conditions and the prolonged life of the zoo bears may affect the function of their thyroid gland.