Equine Cushing's Syndrome, Part 1

Why is Cushing’s disease diagnosed so frequently in horses these days? This disease has actually been in the equine population for many years, but generally went unrecognized. There have always been many unexplained cases of laminitis occurring in the winter or early spring when there is little grass, and we have often seen older horses with inexplicably long hair. Cushing’s only seems to be increasing because of a better understanding of the diagnostic tests involved.

Laminitis is one of the more frustrating complications of Cushing’s disease. Chronic cases can take a lot of time and energy to treat and still not respond satisfactorily. Natural medicine provides another toolbox of treatments to help both acute and chronic cases. The goal in natural treatment of Cushing’s disease and Cushing’s-based laminitis is to:

• Provide nutritional support to prevent and reverse damage from circulating free radicals

• Prevent further damage to and encourage healthy laminar attachments

• Return the horse’s metabolism to proper balance.

When managed correctly, with patience and attention to detail, most chronic cases can return to reasonable work. Poorly responsive cases can often be managed and kept relatively comfortable without the use of drugs.

What is Cushing’s disease?

It has been thought that horses, as part of the aging process, get pituitary adenomas (tumors) of the pars intermedia part of the pituitary gland. But texts disagree about how common the true adenoma tumor is. About half the sources feel the actual adenoma is less common and that there is a hyperplasia instead (abnormal and overactive, but not tumor growth, of the cells). Both adenomas and hyperplasia cause similar sets of symptoms. The hyperplasia, however, being a functional disturbance rather than a tumor, may be easier to treat. Many horses respond well to treatment; these cases are probably more functional than cancerous. Horses that do not respond well to treatment may have an actual tumor.

Why Cushing’s disease occurs is not understood. One theory is that chronic stress (from the horse’s younger life) could lead to the development of hyperplasia and then perhaps progress into a tumor. There are no clear answers at this point.

Laminitis that occurs for no outward reason is one of the most serious symptoms of Cushing’s disease. Some of the most refractory cases of Cushing’s-based laminitis occur in the winter, an uncommon season for typical cases. Even the more common summer laminitis, which appears to be caused by overeating grass, can be quite difficult to treat, especially when other clinical signs of Cushing’s are present.

Many horses diagnosed with Cushing’s laminitis are overweight and very easy keepers, sometimes unable to eat more than a small amount of hay each day to control their weight. They generally have cresty necks and fat pads in specific places. The fat pads are typically behind the shoulder blades, on each side of the tail, and along the lumbar area. The fat on the body is often visibly lumpy. In some cases, horses who were previously easy keepers suddenly start requiring more food to maintain body weight. They may maintain their fat pads despite the obvious weight loss.

Stay tuned for parts 3 and 4 in the coming weeks!

Happy Riding!