Insulin Resistance in Horses
There are two major hormonal problems (endocrine disorders) that affect horses. They are Cushing’s disease and equine metabolic syndrome (EMS). Both these disorders are important because they predispose horses to laminitis. Middle-aged or older (>15 years) horses are more likely to suffer from Cushing’s disease, whereas EMS first develops in younger animals. Obesity and insulin resistance (IR) are related because fat accumulates within cells and interferes with insulin signaling.
Insulin is a hormone produced by the pancreas that stimulates movement of glucose into insulin-sensitive tissues. These tissues become less responsive when IR develops, which slows the rate of glucose uptake. IR may increase the risk of laminitis by compromising blood flow to hoof tissues. Insulin normally dilates blood vessels, so insulin-resistant horses may have difficulty maintaining adequate blood flow to the feet, particularly when this system is challenged.
Cushing’s disease horses are predisposed to laminitis, particularly when accompanied by IR. Cushing’s disease can be diagnosed by blood test. The blood test will show the resting adrenocorticotropin hormone (ACTH) concentration. A high ACTH concentration indicates that a horse has the disease. Cushing’s disease can be medically managed by administration of a prescription of pergolide for the rest of the horse’s life.
EMS refers to a clinical syndrome of obesity, IR, and laminitis. Horses first develop physical characteristics when they are young and then become more susceptible to laminitis over time. Horses that are too fat (obese) are more likely to be insulin resistant, so it is better to maintain horses in a leaner body condition. It is important to recognize that obesity and IR often occur together. Some physical appearances of the horse can indicate a problem with IR are thick neck crest filled with fat, fat pads near the tail, or fat accumulation within the sheath or mammary gland regions. This can be treated by exercise and diet.
If you have any questions regarding this or any other issues your horse may be having, please contact our office at 505-869-2627.