Improving Cushing’s Syndrome or PPID in the Horse

Cushing’s disease in the horse, or PPID, is an ever increasing health problem.  What was once limited to those horses of age, generally over the age of 20, is now being diagnosed in much younger animals. While there are therapies and medications available, the cost can be high as are side effects.  Truth be told, these medications are not addressing the root issue of Cushing’s disease in the horse, thus many horses require higher and higher doses of medications while also continuing to deteriorate in their health.  Let’s look at how you can enhance your Cushing horse’s health, while potentially doing the same thing as what medications offer.

Cushing’s disease or PPID in the horse is essentially a condition of the hypothalamic-pituitary-adrenal axis or HPA axis.  Each organ regulates the next and its function.  The hypothalmus regulates pituitary function and the pituitary regulates adrenal function.  In Cushing’s disease or PPID in the horse, there is a decreased production of the neurotransmitter called dopamine, which helps to regulate pituitary function.  As levels of dopamine drop, the pituitary often goes unregulated, producing high levels of ACTH, which can stimulate the adrenal gland to produce more hormones like cortisol.  Additionally, an adenoma or benign growth is often found within the pituitary gland of the horse with Cushing’s, which is believed to be a result of improper regulation by dopamine.

The ultimate root problem is a lack of dopamine production, but simply supplementing dopamine is not necessarily the solution.  The true solution lies in improving nerve function, while combating inflammation.  This nerve inflammation or degeneration is what results in reduced dopamine production.  If you just supplement dopamine, you are missing the underlying problem of inflammation and oxidative stress damage.

Pergolide Therapy in the Cushing’s Horse

The traditional approach to PPID or Cushing’s disease in the horse is through the use of a medication called Prascend or Pergolide.  This medication was originally used in Parkinson’s syndrome patients to enhance their dopamine production, which is not too dissimilar in pathology than PPID in the horse.  While Pergolide did have benefits in some human patients, the side effects led to the drug being out of favor for therapy.

Pergolide is a dopamine receptor agonist, which means that it acts like dopamine and binds to and stimulates dopamine receptors in the brain.  The use of Pergolide in these cases of Cushing’s disease results from the belief that decreased dopamine production is the true cause.  This is not the case, but only secondary.  It would be like seeing a car that keeps running low on gasoline and believing the solution is to keep dumping in fuel, while not seeking out the leak.

The problem with this approach is two fold in the horse with Cushing’s disease from my point of view.

First, it is not addressing the underlying root problem of inflammation and nerve (brain) damage.  If you do not address this, then the problem continues forward and progressively gets worse.  This explains why many horses require higher and higher doses of the medication Pergolide to achieve benefits.

Second, through the use of this medication, it is very possible to overstimulate dopamine receptors, which can result in side effects.  In human Parkinson’s patients, this is referred to as dyskinesia, resulting in increased tremors or other abnormal movements.  In the horse, what we often see is referred to as the “Prascend veil” where the horse can become lethargic, sleepy, lose weight and have a decreased appetite.  It is not uncommon to also see behavioral changes in theses patients as well.

Many horse owners are using the medication Pergolide daily, often with no improvement and side effects.  A change in the approach is needed.

Another Perspective on Cushing’s Management in the Horse

At this time, traditional therapies are targeting dopamine in the Cushing’s horse.  The decreased production of this neurotransmitter is a major part of the condition, but does it mean medications are needed?

There are many herbs, which are plants or foods, which naturally produce the hormone called L-Dopa.  This is a precursor to dopamine and used by the body to produce dopamine.  You cannot supplement pure dopamine in the horse or person simply because it cannot cross over the blood-brain barrier and get to the brain where it is needed.  Using L-Dopa or ideally an herb which offers L-Dopa naturally is an interesting concept.

Mucuna pruriens is a bean and has been used in alternative medical pathways for centuries for overall health and nervous conditions, including Parkinson’s support.  Mucuna pruriens is also one of the foods or herbs which offers the highest levels of L-Dopa naturally, usually around 4-5%.  Mucuna pruriens has been evaluated in clinical research with Parkinson’s patients with interesting results, usually either equaling the effects of medications or exceeding them, with no evidence of overload or side effects.

Going further, what you need to do is evaluate the physiology of PPID or Cushing’s disease in the horse.  The bottom line problem is oxidative stress and inflammatory changes within nerve tissue which secrete dopamine and other neurotransmitters.  Keep in mind that this oxidative stress problem is usually not just localized to the nerve tissue but is impacting your horse throughout their entire body from joints to their immune system.  In fact, a high percentage of PPID or Cushing’s horses are metabolic syndrome patients and have been for quite some time.  This is pure evidence of disease progression over time which is not controlled or managed properly.  The inflammation associated with metabolic syndrome progresses and eventually impairs nerve and brain function in the horse, resulting in a higher predisposition to PPID or Cushing’s disease.

As a veterinarian, herbalist and researcher, I look at these problems and dig deep into research. Inflammation and oxidative stress, along with underlying metabolic pathways are our target.

In addition to the herb Mucuna puriens mentioned above, there are many other herbs and nutrients which have been explored in Parkinson’s patients, nerve health, and dopamine production.  Two which are very interesting to me personally are exogenous ketones (beta-hydroxybutyrate) and the amino acid Acetyl-L-Carnitine.

Exogenous ketones have been used in our equine patients with metabolic syndrome and act to provide the cell with an alternative energy source, thus restarting the engine so to speak, and assisting in metabolism and weight management.  Exogenous ketones like beta-hydroxybutyrate can be highly effective when used properly.

Acetyl-L-Carnitine is another heavily researched amino acid which can benefit fat metabolism, but also serves as a potent antioxidant, protecting and often restoring nerve and brain function.  It is heavily researched in human medicine and proven beneficial in Parkinson’s patients.

Going further, there are many other herbs which provide antioxidant and anti-inflammatory support, while targeting nerve function.  This list includes Ganoderma lucidum (Reishi), Olive leaf extact, Hericium erinaceus (Lion’s Mane), Ashwagandha, and Bacopa.

Ideally, you do not just use one of these herbs or therapies, but combine them together for synergism.

This combination is now available in the SV EQ Cushing’s Support herbal blend.

One thing to keep in mind is that it is not recommended to use the herbal formula which contains Mucuna pruriens along with the medication Pergolide or Prascend.  The reason is that usage of both may overload the dopamine receptors and dopamine production, which could result in side effects potentially.  It is not a combination that we have explored and is not used in human medicine with Parkinson’s patients.

Given the high usage of Pergolide in Cushing’s horses and even those that are not true Cushing’s patients, it becomes a personal decision as to continue forward with medications or seek out other options that may prove equally effective and benefit your horse on a whole-body level.

Want to keep your horse on Prascend or Pergolide, but get the benefits of the SV EQ Cushing’s Support formula without the potential interaction of Mucuna puriens?  Try the SV EQ Cushing’s Support II formula!

Author:  Tom Schell, D.V.M, CVCH, CHN