Some aspects of lipid metabolism and thyroid function in arctic ground squirrel, Citellus parryi during hibernation.

The increased blood levels of thyroid hormones as well as morphologic signs of high activity of thyroid gland were observed in arctic ground squirrel during hibernation. High thyroid activity could explain the characteristics of lipid metabolism observed in the studied species during hibernation-increased lipid unsaturation and decreased cholesterol/phospholipids molar ratio in plasma membranes. High blood concentrations of total lipids, cholesterol, and phospholipids in dormant animals is explained by the dissociation between thermogenic and lipotropic actions of thyroid hormones. We postulate that thyroid hormones participate in long-term regulation of body energy metabolism and of homeoviscous adaptation of membranes during hibernation.