The medication levothyroxine sodium appears to protect horses against endotoxemia-induced insulin resistance, reported a group of top U.S. researchers and equine internists.

"Previous studies have demonstrated that endotoxemia results in a transient insulin resistance in horses. Therefore, if horses and ponies undergo a carbohydrate overload when turned out onto lush, green pastures in the spring and endotoxemia occurs, then horses that are already insulin resistant may have increased risk of laminitis," explained lead researcher Nicholas Frank, DVM, PhD, Dipl. ACVIM, associate professor in the Department of Large Animal Clinical Sciences at the University of Tennessee's College of Veterinary Medicine.

To assess the impact of dexamethasone or levothyroxine sodium on glucose and insulin levels in horses with experimentally-induced endotoxemia, the researchers fed some of the 24 horses either dexamethasone or levothyroxine sodium powder in mixed with oats once daily for 15 days. An intravenous infusion of lipopolysaccharide (LPS) was then administered to induce endotoxemia. They assessed changes in insulin sensitivity via glucose tolerance tests and measured glucose and insulin blood concentrations. Horses suffered only transient illness in response to the endotoxin administration.

"A decrease in insulin sensitivity was observed in all horses during hospitalization prior to administering the lipopolysaccharide," said Frank. "This indicates that hospitalization negatively affects insulin and glucose dynamics