Hormonal (Endocrinopathic) Laminitis

Eleanor M. Kellon, VMD

Laminitis caused by high insulin is different from other types.

There are many causes of laminitis, including dietary overloads, hormonal disruptions, toxic plants, severe intestinal disorders, and bacterial infections. It has been estimated that 80% or more of laminitis cases fall under the category of hormonal/endocrine pathologies; until recently,  however, detailed research has focused on other causes. Hormonal laminitis is different.

Research has shown that both toxic laminitis (black walnut) and hind gut carbohydrate overload (starch/fructan) are characterized by activation of tissue degrading matrix metalloproteinase enzymes (MMPs), breakdown of the basement membrane, and inflammation revealed by large numbers of invading neutrophil white blood cells.

However, studies over the past few years have shown that this does not happen with laminitis caused by high insulin, which may have a lot to do with why this type of laminitis does not respond particularly well to antiinflammatory drugs like phenylbutazone. The cascade of tissue destruction caused by inflammation does not occur in laminitis related to this hormonal disruption.

We do not yet understand the complete mechanism behind endocrinopathic laminitis but there are important clues.  High levels of insulin lead to high levels of endothelin-1, an extremely potent vasoconstrictor that interferes with blood supply to the laminae. A large body of literature also links insulin resistance and oxidative stress, high levels of reactive oxygen species.

With acute endocrinopathic laminitis, the core of treatment is to reduce the simple sugar and starch content of the diet by feeding only low-sugar/starch hay and supplements as needed to balance the minerals in the hay, fed in a low-sugar/starch carrier such as rinsed and soaked beet pulp, soybean hulls, or Brewer’s/Distiller’s dried grains.

Potent antioxidant supplements containing both plant-based sources like Devil’s Claw, and nutrient sources like N-acetyl-cysteine, vitamin C, lipoic acid, and vitamin E, work just as well, if not better, in controlling pain in acute episodes compared to nonsteroidal antiinflammatory (NSAID) drugs and without the potent side effects.

Supporting blood flow to the hoof in the face of high endothelin-1 concentrations is also important. The herb Jiaogulan (Gynostemma pentaphylluma), is an extremely potent vasodilator. It is well accepted by horses, and is safe and effective in relieving pain in a high percentage of laminitic horses.  It works by stimulating production of the vasodilator nitric oxide inside vessels.

Endothelin-1 levels are even higher in horses with chronic laminitis pain, so nitric oxide support is indicated for these as well, in addition to meticulous attention to diet and an appropriate trim.

There are also chronic cases where pain is contributed to by actual changes in the nerves and the spinal cord — neuropathic pain. Acetyl-L-carnitine, (ALCar), is a naturally occurring metabolite of L-carnitine in the body, and has shown clear benefit in different types of  neuropathic pain in many species. It has also been effective in horses.

We have much more to learn about hormonal laminitis but have made decent inroads and the most important realization for moving forward is that this is different from other causes of laminitis. The solutions need to be different too.

For more information go to ecirhorse.org.

About ECIR Group Inc.
Started in 1999, the ECIR Group is the largest field-trial database for PPID and EMS in the world and provides the latest research, diagnosis, and treatment information, in addition to dietary recommendations for horses with these conditions. Even universities do not and cannot compile and follow long term as many in-depth case histories of PPID/EMS  horses as the ECIR Group.

In 2013 the Equine Cushing’s and Insulin Resistance Group Inc., an Arizona nonprofit corporation, was approved as a 501(c)3 public charity. Tax deductible contributions and grants support ongoing research, education, and awareness of Equine Cushing’s Disease/PPID and EMS.

THE MISSION of the ECIR Group Inc. is to improve the welfare of equines with metabolic disorders via a unique interface between basic research and real-life clinical experience. Prevention of laminitis is the ultimate goal. The ECIR Group serves the scientific community, practicing clinicians, and owners by focusing on investigations most likely to quickly, immediately, and significantly benefit the welfare of the horse.

Contact:  Nancy Collins

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