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Equine Metabolic Syndrome: Explanations and Possibilities

Dr. Joseph Thomas, For Love of the Horse

Equine Metabolic Syndrome is the new medical label for what has previously been known as Cushing’s disease. This is more than just a fancy name change. From a theoretical and therapeutic frame of reference, the new label is far more accurate. By naming it a metabolic syndrome, the underlying systemic problems that exhibit the whole host of symptoms that are associated with Cushing’s disease are addressed. This understanding opens viable directions for new concepts in treatment. Furthermore, it offers insight into the connection between Cushing’s and Laminitis – a connection that has long been known but not understood.

To Need or Not To Need a Tumor

Within the veterinary and research world, the presence of a tumor (adenoma) located in the intermediate lobe of the pituitary gland (marble-sized gland that sits at the base of the brain) has been assumed to exist in horses, as it does in humans, known to have Cushings. The tumor is a definite possibility in humans, yet this belief has stubbornly persisted with horses, despite the large number of horses suffering from this disease and the unlikely possibility that all of them had developed tumors. In fact, the tumor notion in horses is quite unlikely.

A few researchers have recently proposed other more viable explanations of this syndrome. Both Dr. Nat Messer and Dr. Philip Johnson of The University of Missouri’s Department of Veterinary Medicine and Dr. Chris Pollitt, director of The Australian Equine Laminitis Unit of The University of Queensland, Australia have presented metabolic models that do not require a pituitary tumor to explain the occurrence and progression of Cushing’s. Dr. Pollitt’s research suggested rather than a tumor in the intermediate lobe of the pituitary gland what was actually being seen, more than frequently, was an enlargement of this particular area of the pituitary. The enlargement is enough to create a dysfunctional pituitary gland that would clearly set up the necessary underpinnings for Equine Metabolic Syndrome.

Metabolic Syndrome Explained

Equine Metabolic Syndrome is highlighted by an aberration in the critical feedback loop that exists between the Pituitary Gland and the Adrenal Glands (which functionally sit on the kidneys). The pituitary gland secretes a hormone labeled ACTH (adrenal corticotrophic hormone) and the adrenal glands secrete a hormone labeled Cortisol. The delicate dance between these two glands and the hormones they produce is at the root of the Cushing’s and Laminitic metabolic explanation.

The pituitary hormone ACTH manages the quantity of cortisol that is released into the bloodstream by the adrenal glands. The pituitary gland monitors the cortisol’s magnitude and stops the production of ACTH when a “healthy” level of cortisol (or excess) is present in the blood. The pituitary will manufacture more ACTH when an increase in cortisol is needed. The pituitary gland’s job, in this arena, is to insure that cortisol levels are exactly where they should be for a healthy metabolic system.

However, this pituitary-adrenal gland feedback loop, in a horse with Equine Metabolic Syndrome is not working appropriately. The pituitary gland continues to produce ACTH even though there is clearly a pathological overabundance of cortisol in the bloodstream. The adrenal glands response to ACTH production is always going to be to make more cortisol thereby escalating the already present metabolic problem.

The figures above graphically illustrate this metabolic process.

Treatment of Equine Metabolic Syndrome

An Overabundance of Cortisol

An overabundance of cortisol disrupts insulin’s function of assisting cells in the absorption of glucose. Glucose is essential as cells’ fuel, their “life force;” if you will. Given a breakdown in the healthy relationship between glucose, insulin and cells, there quickly becomes an excess of glucose in the blood which signals the production of more insulin to take care of the surfeit glucose, only exacerbating the present problem by increasing the overload of insulin.

Possible Changes in Laboratory Blood Work

There is likely to be a high to above “normal” concentration of glucose, insulin, cortisone (cells store cortisol in this molecular form) and ACTH in the blood of a horse with Equine Metabolic Syndrome. The levels of all these substances vary throughout the day following a natural circadian rhythm. This very important rhythmic process must be taken into consideration when doing blood analysis on a horse with a metabolic problem to avoid erroneous interpretations.

· hair coat grows unnaturally long and does not shed until considerably past the time when other horses have already lost their coats

· immune system affected – possibly leading to respiratory and skin infections and definitely an increase in the frequency of hoof abscesses and sole bruising

· a serious drop in energy level that increases without treatment

· depression

· increased risk of colic

· loss of muscle tone

· a definite increase in risk of laminitis

· an inordinate increase in urination and thirst

From a Contemporary Chinese Medical Model

The principal herbs in the “Cushings” combination that I have developed address the pituitary-adrenal feedback loop to restore the functional integrity of the relationship between ACTH and Cortisol. No metabolic change of any benefit will be produced unless this feedback loop is returned to a healthy communication.

The Yang aspect of the kidneys rules the adrenal glands and the pituitary gland is directed by the Yin aspect of the kidneys. To return this feedback loop to healthy communication, each of these aspects must be properly supported and directed to the adrenals and the pituitary gland. In Chinese herbalism individual herbs must be combined in groups with specific functions and synergistic relationships in order to achieve this equilibrium. One such group, in this metabolic, herbal combination, called the Chief Ingredients, is Fu zi, Rou gui and Lu jiao jiao. Together these three herbs supplement the Yang aspect of Kidneys effectively restoring the adrenal glands and decreasing the production of cortisol. Another group of herbs (Shu di huang, Shan zhu yu, Shan yao, gou qi zi, tu si zi, and du zhong) nourish the yin of the kidneys, thereby supporting the regulatory function of the pituitary gland. These herbs also support the effectiveness of a third group of herbs that nourish the spleen and pancreas (makes insulin) to assist in a healthier absorption of glucose.

When herbs are mixed from an elegant theoretical base, they speak in a language that the body understands from an intrinsic core. These herbs direct the horse’s body to establish a healthy feedback loop to allow the cells to absorb glucose. In all there are nineteen different herbs combined in this formula. Individually and in combination they address the metabolic dysfunction that underlies what used to be called Cushings and is now Equine Metabolic Syndrome.

About the Author:

Joseph Thomas, PhD, DiplAc has been a teacher, consultant, and practitioner of Chinese Medicine for more than twenty years. Before practicing Chinese Medicine, Joseph was on the research staff of the Massachusetts Institute of Technology’s Department of Psychology and Brain Science. He has devoted his skills and knowledge to the development of sophisticated herbal solutions for horses based on the elegance of Chinese Medicine. Dr. Thomas is available for consultations and may be contacted at For information on the current product line, visit his website at:
For Love of the Horse