Cushing's Disease, Insulin Resistance  and
"Tamera"

Tamera
Tamera when she was 8 years old.
Tamera was four years old when she became a part of my life.
  In February of 2000, she was diagnosed with Equine Cushing's disease,  she had just turned 24.

My version of Equine Cushing's 101

Cushing's disease is caused by a benign tumor of the pituitary gland. The pituitary gland is a small gray gland attached to the base of the brain. It is often referred to as the master gland of the body, since the hormones it secretes regulate many body processes, including TSH, a thyrotropic hormone which regulates the thyroid and ACTH (Adrenocorticotrophic hormone) which regulates the adrenal glands.

The most common symptoms are:
  • Sudden-onset polydipsia. An affected horse may drink as much as 80 liters of water a day (as opposed to an average 20 – 30 liters). This is accompanied by frequent urination
  • Abnormal hair growth and shedding. Affected horses may develop a growth of heavy, coarse, often curly hair, which does not shed in the summer. This is usually accompanied by sweating
  • Development of a swayback stance and a pot belly
  • Filling above the eyes caused by the deposition of fat
  • A general appearance of malaise, depression, with dull eyes and drab coat
  • Increased appetite (usually with no accompanying weight gain)
  • Chronic laminitis (inflammation of the lamina of the hooves, can cause coffin bone to rotate, commonly referred to as founder)
  • Loss of muscle over the topline
  • Compromised immune system. This makes the horse susceptible to a myriad of conditions/diseases which are often passed off as old age. These include respiratory disease, skin infections, abscesses of the foot, buccal ulcers, and periodontal disease
  There are several tests to diagnose Cushing's but the safest in my opinion is a serum ACTH.

Common medications for the treatment of Cushing's are:
Cyproheptadine (Periactin) and  Pergolide Mesylate (Permax)
Cypro has taken a back seat to pergolide in the treatment of cushings.  Pergolide is far superior in managing the symptoms of cushings.
The herb chastetree berry (vitex agnus castus) seems to have positive results in many horses at least for awhile, but ultimately these horses will need pergolide.

Managing Cushing's
  • Avoiding stressing the horse. The hormonal profile of many horses with Cushing’s already indicates high stress levels, so reducing stress is critical
  • Providing a safe, comfortable “sanctuary” for the horse
  • Sticking to a strict routine, which will help minimize stress
  • Keeping water and feed conveniently located and in the same place
  • Clipping the horse in warm weather; using blankets when it is cold
  • Keeping up grooming to minimize skin diseases
  • Maintaining good hoofcare
  • Checking teeth regularly and having them checked by a professional twice a year
  • Avoiding turning the horse out with aggressive horses
  • Avoiding contact with horses from a new location
  • Keeping immunizations to a minimum/ making sure all necessary shots are given
  • Deworming regularly
  • Providing an appropriate diet for the horse. This usually involves elimination of simple carbohydrates
Insulin Resistance (IR)

Insulin is a hormone secreted by the pancreas in response to blood sugar.  It signals the cells to take up glucose (all sugars and starches in the diet are converted to glucose before being absorbed).

Diabetes in people comes in two types, type I and type II – also called insulin dependent (type I) and non-insulin dependent (type II).  In type I, the pancreas does not secrete enough insulin.  These are the people that require insulin injections.  In type II, the insulin secretion is fine but the cells do not respond to it normally.  This is “insulin resistance” – i.e. the cells are resistant to the effects of insulin.

Insulin Resistance in horses is very similar to type II diabetes in humans. To determine if your horse is Insulin Resistant, have your vet draw a glucose and an insulin blood level. Once you have these results then you can calculate the insulin: glucose ratio. Your insulin & glucose results need to be in the proper units to determine this ratio.  Insulin in IU/L or U/L and glucose in mg/dl. Some labs use different measures. If your insulin results are in pmol/L divide this number by 7.1 to get IU/L results. If your glucose results are in mmol/L multiply this number by 18 to convert to mg/dl. Once you are in the proper units simply divide the glucose by the insulin number. A number below 4.5 is considered Insulin Resistant.

Symptoms of IR
While not all overweight or obese horses are IR, that is one of the earliest symptoms. Watch those easy keepers carefully. Development of prominent fat deposits on the crest of the neck, at the tail base, along the withers or at other locations is also common. Occasionally, thinner horses can also be IR, as in Tamera's case.

IR  horses and ponies are at high risk for developing repeated problems with laminitis and it has been acknowledged that IR is a pre-disposing factor to laminitis. The exact mechanism for the laminitis is unknown, but likely related to the circulatory and inflammatory changes that are known to go along with IR in other species.  Over time this can develop into life threatening cases of founder.
Tamera had one episode of laminitis in October of 2000. I was devastated, as she had never been lame a day in her life. At that time we were giving her cyproheptadine for her Cushing's. We switched her over to pergolide, which she still receives. New Year's Eve that year Tamera received her first Strasser trim. (If you want more information on Dr. Strasser, go to our link page). She is trimmed every four weeks religiously, just like the rest of our horses. As of this date Tamera has not had a recurrence of laminitis. I attribute this to her diet, pergolide, good hoof care and a lot of luck. Many of us take our horse's hooves for granted. I, for one, will never do that again.

Tamera and the IR diet
 
The only way to manage IR is through strict diet. Feeds high in non-structural carbohydrates (NSC)should be avoided. I stay away from any feed that has a NSC higher than 10%. We have our hay analyzed and we are very fortunate that the NSC has always tested below 10%. The ideal feed for her would be this low starch/sugar hay. However, Tamera is unable to grind hay because there is no enamel left on her teeth. While she tries to chew hay, which I still offer her, she doesn't seem to ingest much.
These last years, keeping weight on Tamera has been quite a challenge.   Her main diet consists of soaked Lakin-Lite pellets (alfalfa-bermuda blend).  Again, we are very fortunate that the Lakin-Lite pellets have always tested low in NSCs. I also feed her well rinsed/soaked beet pulp. I balance the phosphorus in her beet pulp with stabilized flax seed. Although there has been literature refuting the belief that feeding beet pulp dry can cause choking, I still prefer to feed beet pulp wet.   In addition to her pergolide and thyroid medication, her supplements include Springtime GL (glucosamine hydrochloride), Magnesium Oxide, Vitamin E 2000 IU, Horseshine (flax). I also feed Tamera cinnamon, as it lowers insulin levels. We also have a custom mineral mix  formulated by Dr. Kellon specifically for the Lakin-Lite pellets. All my horses' diets are reviewed regularly by Dr. Eleanor Kellon, a well known expert on Equine Nutrition (if you are not familiar with her , just do a search on her). I consider her our horses' fairy godmother.

Please remember, this is what works best for Tamera. If you have a horse with Cushing's or IR I highly recommend joining the Equine Cushing's Yahoo group: http://groups.yahoo.com/group/EquineCushings/. Boasting over 5500 members this is possibly the largest equine group on line. The folks in this group are extremely  knowledgeable and very supportive, an added bonus is that  Dr. Eleanor Kellon   is co-owner of this list. Her support and guidance to these horse owners is commendable. She is an invaluable advisor and friend to us all.


My Tamera, July 1 2006.







Tamera in March of 2007....giving me a kiss and then playing with Freddie & Sumer




                  


Me and "Tams" again.....
 Kisses are like potato chips... one is never enough !!!!!!

On June 2, 2007 our beloved Tamera was euthanized due to anhydrosis (the inability to sweat).
She had suffered from this condition for several years, but surviving one more AZ summer was not in the cards for my sweet girl. She passed peacefully and with dignity surrounded by her loving family.
This page will remain a tribute to my sweet Tamera and all that she taught me.


                                                               


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