Peripheral Cushing's ( Equine Metabolic Syndrome )
Middle aged horses that accumulate fat in the crest of the neck, over the rump, and in the sheath may have Equine Metabolic Syndrome. This is a
hormonal disease caused by overproduction of an enzyme produced by fat cells resulting in elevated cortisol in the body tissues. This enzyme is called
hydroxysteroid dehydrogenase (HSD) and has also been identified in humans with Omental Cushing’s Syndrome. EMS differs from Equine Cushing’s Syndrome
(PPID) in that pituitary gland function is normal in EMS and abnormal in ECS. The elevated cortisol in both diseases causes insulin resistance, slightly
elevated blood sugar, and then vascular disease that can lead to laminitis. Thyroid function is normal although more common lab measurements may be
artificially decreased leading to a false diagnosis of hypothyroidism.
Diagnosis of EMS requires a fasting blood sugar and insulin test. At the same time, suspect horses should be tested for Equine Cushing's Syndrome
because of the similarity in external clinical signs of the two syndromes. A complete blood panel should be done to check blood cells organ function
and serum electrolytes.
Treatment of EMS includes strict weight reduction and the avoidance of dietary carbohydrates that can trigger weight gain and laminitis.
Horses should principally be fed grass hay until body weight is controlled. Ideally, the hay should be tested for carbohydrate content (WSC—water soluble
carbohydrates like starch and sugars should be under 12, NSC under 15). No oat or wheat hays should be used. Hay should be fed at 1.5% of desired body weight or
less, and the horse should be measured with a weight tape once a month until the desired weight and body condition score are met. Initially to reduce obesity,
thyroid hormone may be used to increase the body weight and decrease weight, but the veterinarian will need to monitor heart rate and weight in these horses, and
taper the medication slowly. Horses should not be allowed access to pasture until laminitis is in control. Thereafter, access should be controlled and allowed only
as directed during early morning hours. One pound or less per day of Triple Crown Lite or other low starch feeds (Sound Starch, Senior) may be given in lieu of 1
pound of hay. A balanced vitamin-mineral supplement should be given daily in a granular form (Ranch-O-Min 1011, Purina 12-12+ or Grostrong Minerals) at one ounce
twice daily. Free choice water and white salt (block or coarse granular form) should be offered.
Recent research shows that the addition of 10,000 mg of Vitamin C and 5000 IU of Vitamin E daily has an antioxidant effect, which is therapeutic in treating inflamed
hoof laminae, and improves the immune status of stressed horses.
In selected cases, a thyroid hormone supplement may be used to aid in weight reduction, but monthly weight tape and heart rate measurements must be done.
Lameness issues, if present, should be addressed with appropriate shoeing and anti-inflammatory medication as prescribed. Once the horse is comfortable, regular
exercise will improve insulin-glucose balance and help control obesity.