Cushing’s Disease & Metabolic Health

SmartPak strongly encourages you to consult your veterinarian regarding specific questions about your horse's health. This information is not intended to diagnose or treat any disease, and is purely educational.

Brief Description

Cushing’s Disease is a dysfunction of the pituitary gland, and is most common in older horses (18 – 23 years). Since it is sometimes associated with Insulin Resistance, Cushing’s Disease can be confused with another condition called Equine Metabolic Syndrome. For more information on Equine Metabolic Syndrome, click here.

• Hirsutism (long, curly hair that resists shedding)
• Weight loss and muscle wasting
• Lethargy and poor performance
• Normal to increased appetite
• Fat deposits, especially along the crest of the neck and over the tail head
• Becoming overly docile and tolerant of pain
• Subtle onset of laminitis
• Increased drinking and urination
• Increased infections with delayed wound healing

Supplements that May Lend Support

The following types of supplements may be helpful in the management of Cushing’s Disease and are often considered beneficial for senior horses in general:

• Antioxidants and plant adaptogens to fight oxidative stress and provide immune support
• Amino acids such as lysine, methionine and threonine to support lean muscle mass
• Prebiotics, probiotics, yeast, and enzymes for digestive support
• Weight Gain or fat supplements for those horses that lose weight

In cases where the horse has Insulin Resistance in addition to Cushing’s Disease, specific supplements that help manage proper insulin and blood sugar metabolism may be beneficial. One such product is SmartControl IR, and additional supplement suggestions can be found on the Equine Metabolic Syndrome page.

Possible Diagnostic Tests

After a complete physical examination and routine bloodwork (CBC and serum chemistry), your veterinarian has a few options for specifically diagnosing Cushing’s Disease. These include the dexamethasone suppression test, measuring ACTH concentration and others. Avoid having these tests done in the fall, as results can be falsely positive.

Prescription Medications Available

Pergolide and cyproheptadine are used separately and sometimes together, in particularly difficult cases, to manage Cushing’s Disease. Since neither is FDA-approved for use in horses, this is considered “extra-label” use.

Other Management Suggestions

Diet

Because insulin and blood sugar metabolism may not be functioning properly in Cushing’s horses, avoid feeding traditional grains, treats or pasture because these can be high in sugars and starches. Instead, meet the horse’s nutrient requirements with a multi-vitamin/mineral supplement or low-sugar/high-fiber feed made especially for senior horses. Add fat for additional calories, if needed.

General

An older horse with Cushing’s Disease is truly a “special needs” horse. Cushing’s often compromises the immune system, causing horses with this condition to be more prone to infections, laminitis and other health problems. Because of this, Cushing’s horses should be seen by a veterinarian at least twice per year, with special attention paid to vaccinations, deworming, dental health, hoof care and other preventive maintenance.

Questions to Ask Your Veterinarian

• How is Cushing’s Disease different from Equine Metabolic Syndrome and Insulin Resistance?
• Is Cushing’s Disease the same thing as diabetes?

Additional Resources

Further Reading for You

From our site:

Equine Cushing’s Disease vs. Equine Metabolic Syndrome

From the SmartPak Ask the Vet Blog:

Supplementing Chronic Conditions in the Senior Horse
Diet Considerations for Horse with Cushing's

From The Horse Journal:

• Cushing’s or Not, Attack Insulin Resistance, October 2002
• Time Your Cushing’s Tests, May 2005
• Is He Really Cushing’s or Just Fat and Hairy?, March 2003

Further Reading for Your Veterinarian

Schott HC. Pituitary Pars Intermedia Dysfunction: Challenges of diagnosis and treatment. In: Proceedings of the 52nd Annual AAEP Convention; pp 60-73.

Ralston SL. Care for the Older Horse: Diet and Health. In: Recent Advances in Equine Nutrition. Ralston SL and Hintz HF, editors. Ithaca: International Veterinary Information Service (www.ivis.org), 2001.

Donaldson MT, McDonnell SM, Schanbacher BJ, et al. Variation in plasma adrenocorticotropic hormone concentration and dexamethasone suppression test results with season, age and sex in healthy ponies and horses. J Vet Intern Med 2005;19:217-222.


About Dr. Lydia Gray