Insulin Dysregulation in Horses with Systemic Inflammatory Response Syndrome

Background: Systemic inflammation is a cause of insulin dysregulation in many species, but the insulin and glucose dynamics in adult horses diagnosed with systemic inflammatory response syndrome (SIRS) are poorly documented.

Hypothesis/objectives: In SIRS in horses, insulin and glucose dynamics will be altered and associated with survival.

Animals: Adult horses diagnosed with SIRS admitted to a referral hospital.

Methods: Prospective study enrolling horses diagnosed with SIRS in which serum insulin and glucose concentrations were measured. Horses were grouped by outcome (survival, hyperinsulinemia, and hyperglycemia) and compared with P < .05 considered significant.

Results: Fifty-eight horses were included in the study and 36 (62%) survived. At admission, 21 horses (36%) were hyperinsulinemic and 44 horses (88%) were hyperglycemic, with survivors having significantly higher serum insulin and a significantly lower serum glucose concentration. Horses diagnosed with hyperinsulinemia at any time during hospitalization were 4 times more likely to survive whereas horses that were hyperglycemic at any time during hospitalization were 5 times less likely to survive. Serum glucose concentration and presence of hyperglycemia both were associated with severity of disease. Insulin/glucose ratio, reflecting insulin secretion, was significantly higher in survivors whereas glucose/insulin ratio, reflecting peripheral tissue insulin resistance, was significantly lower in nonsurvivors. Only in survivors was there a significant correlation between serum insulin and glucose concentrations.

Conclusions And Clinical Importance: Hyperinsulinemia and hyperglycemia are common features of SIRS in horses, but those presenting with relative hypoinsulinemia and corresponding hyperglycemia suggestive of endocrine pancreatic dysfunction have a worse prognosis.