Insulin Resistance / IR (Insulin Dysregulation)

A failure of normal insulin concentrations to stimulate tissues to take up glucose from the blood. When the normal concentration of insulin fails to lower blood glucose properly, the pancreas reacts by producing more insulin to compensate. The normal resting blood insulin level rises (hyperinsulinemia) pushing glucose into the tissues and so blood glucose tends to stay within normal range with insulin above normal resting levels. This is called compensated IR as some measure of control is still being maintained.

If the stimulus of high blood glucose persists due to continuing high dietary starch / sugar levels, the pancreas may become exhausted and insufficient to control blood sugar. The high initial blood insulin level will fall as the pancreas becomes insufficient and blood glucose rises in response and remains above normal. This is called uncompensated IR and may be a result of PPID/ Cushings Disease. Insulin Resistance is also a part of Equine Metabolic Syndrome.

Causes of IR include a genetic predisposition, an above average efficiency of energy metabolism seen in ‘’easy keepers’’, uncontrolled obesity, overfeeding and high starch / sugar levels (high NSC)  in the diet. Diagnosis may be assisted by screening tests for blood glucose and insulin and specific tests involving administration of a sugar or glucose dose followed by monitoring responses with further blood tests. This is called a Glucose Tolerance Test. Adjunct testing for EMS / PPID may be warranted also.

Treatment and management of the condition revolves around controlling NSC intake, weight loss diets, avoidance of laminitis to which these horses are predisposed, and increased exercise. A diet and exercise plan developed under veterinary supervision is key.

In broodmares IR has been demonstrated to have impacts on the developing foetus during pregnancy which render it more prone to developing IR after birth which in turn increases the risk of the foal developing Developmental Orthopaedic Disease, and OCD. For this reason, avoiding the condition in broodmares by managing NSC intake through the use of low starch / low NSC supplementary feeds is becoming accepted stud farm practice.

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