Cushing’s Disease in Horses (PPID)

Cushing’s Disease in Horses (PPID)

Posted by Marijke van de Water on 2018 Sep 22nd

Why is it an Equine Epidemic?

Cushing’s disease is now known as PPID or Pituitary Pars Intermedia Dysfunction. Although I don’t much care for this new term because it implies that it is a pituitary disease rather than a disease of multiple causes associated with Equine Metabolic Syndrome (EMS) including Insulin Resistance (IR).

The pituitary, often called the “master gland” is a small bean-shaped organ that hangs down from the lower centre of the brain. Its primary function is to produce various hormones to stimulate and regulate other body functions, including thyroid and adrenal function. It is interesting to note that the pars intermedia portion of the pituitary is much more developed in a horse than in a human, obviously a sign of its overall importance for the equine.

PPID is so called because it causes the horse's pituitary gland to work over time. A dysfunctional pituitary associated with Cushing’s disease was always thought to be caused from tumours on the gland which caused it to mal-function. But we are learning that this is not the case. Rather, these tumours seem like “enlargements” – all overworked organs will eventually enlarge - and are caused by a cascade of unbalanced hormones disrupted by diet, IR and excess weight. Therefore, these enlargements or tumours or whatever you want to call them are a result of prolonged stimulation of the pituitary which is on a long call of duty during a health crisis.


The onset of PPID is not sudden; it’s a slow development of hormonal changes initiated by the factors mentioned above. Signs and symptoms can vary from horse to horse but PPID and pituitary imbalances most often lead to slow hair coat shedding in the spring and summer, a rough or curly hair coat, excessive sweating, and fatigue or depression. The immune system is usually compromised as well resulting in chronic infections or poor resistance to other diseases. In later stages there may also be muscle wasting. PPID may also be a contributing factor in laminitis especially in the presence of poor diet and nutrition combined with unsuitable trimming practices.

The PPID horse may also have low resistance to stress or poor coping skills. Stress throws off blood sugar levels, contributes to chronic production of cortisol, causes erratic insulin production, results in higher than normal production of adrenaline, and can lead to adrenal burn-out.

While lab tests are available to test insulin, ACTH and other hormone levels they are not always conclusive – endocrine hormones are secreted into the blood in “bursts” rather than in a steady flow making them difficult to track. In addition, there are seasonal variations with a higher production of ACTH in the late summer and early fall. There are also changes in results according to geographic location from north to south.

But it is not necessary to wait for a definitive diagnosis or for clinical signs before implementing common-sense horse-keeping strategies that are sure to improve general health and prevent problems for all horses, no matter the age, breed, or discipline.

The Real Cause of PPID in Horses

From a purely physiological perspective, this over-activity by the pituitary in PPID is caused by the over-production of cortisol by the adrenal glands as caused by high insulin levels. All blood sugar conditions or obesity increase the production of insulin by the pancreas because it is the job of insulin to open up the sugar receptors in the muscles and liver to allow sugars to pass from the blood and enter into the tissues where it is used for energy. This is also what keeps blood sugar levels from rising after eating.

Insulin also however, causes the adrenal glands to increase the production of cortisol and corticosterone – steroid-like hormones that normally combat stress, decrease inflammation and regulate carbohydrate metabolism including blood sugar.

But, elevated cortisol levels have a dark side and when they are too high or high for too long they will actually increase blood sugar, stimulate appetite, depress the immune system, decrease bone density, weaken the muscles, and catabolize connective tissue - including hoof lamina causing laminitis. So you can see why it is SO important to keep cortisol levels under control and regulated within a small margin of safety.

This is the job of the pituitary which, when alerted to high levels of both insulin and cortisol production with a feedback system of communication, is prompted to produce adrenocorticotropic hormone (ACTH). ACTH is required to regulate, i.e. speed up or slow down, the production of cortisol to keep it in balance before it does more harm to other body systems. The problem though is that if the underlying cause of the imbalances in the first place are not corrected the pituitary will continue to work harder.

High sugar diets, lack of exercise, and stress will continue to perpetuate the cycles of excess hormone production. The thyroid often gets involved too because thyroid hormones and the conversion of thyroid hormones (T4 to its active form T3) are suppressed in the presence of high insulin and high cortisol levels.

Conventional Treatment for Equine Cushing’s

Veterinary mainstream ignores the importance of the ever-critical hormone balances and the underlying causes and puts all the blame on the pituitary. The affected horse is then prescribed medication to slow down the production of ACTH and other hormones. But that’s not what the pituitary gland wants to do; it wants to help stabilize the underlying problems that are causing it to ramp up activity in the first place. Blood sugar abnormalities and the imbalances of cortisol and insulin production are the real culprits. Left to its own devices the body will always seek to set up defense mechanisms to optimize function and sustain life.

Horses with PPID produce less dopamine in the brain. Dopamine is a neurotransmitter that helps to regulate the production of pituitary hormones including ACTH, and the less dopamine the more hormones the pituitary can produce. So the brain decreases its production of dopamine enabling the pituitary to step up its production of ACTH. It all works together.

The current medications for PPID act as a dopamine substitute to suppress pituitary hormone production. They do not however, extend longevity and some experts question whether or not they actually improve quality of life. In addition, these medications may cause side effects of decreased appetite, diarrhea, colic, fatigue, weight loss, skin problems, joint or muscle pain, a fast heartbeat, as well as depression and behavioural changes. Medications containing Pergolide were removed from the U.S. market intended for use by people due to serious side-effects and safety concerns.

The Holistic Approach to Equine Cushing’s

PPID is becoming all too common in horses, with a median age a shocking 15 years old! No doubt a testament to inappropriate diets, lack of exercise, and stress, which impacts horses of all ages.

In sharp contrast to the mainstream view, the holistic model maintains that the true and underlying cause of PPID is caused by metabolic problems. Like people, diseases don’t just happen to horses; they are created by lifestyle and the domestic environment.

Diseases don’t just happen to horses; they are created by the domestic environment.

The prevention and treatment of metabolic diseases is nothing more than common-sense horse-keeping: you cannot capture or breed wild animals then domesticate them with a high-sugar or high-protein diet, confine them to a small space, increase their stress levels, and then expect them to be healthy. The equine species has spent centuries surviving on freedom – the freedom to forage, the freedom to make friends, and the freedom to run with the herd. When you take away freedom you create dis-ease.

The most effective natural program to treat PPID holistically, is one that addresses the underlying cause. This is accomplished by supplementing them with the right nutrients and herbal remedies. The correct program will not only provide the nutrition they need to recover but it will also support and repair the endocrine system. After helping thousands of metabolic horses improve their health, I have found that the program below is the most effective for balancing metabolism and promoting normal hormone balance.

Riva's Holistic Horse Program for Equine Cushing's (PPID)

  1. Treat for Insulin Resistance (IR) by changing the diet, increasing exercise, and managing stress levels. Refer to  Insulin Resistance – Diet, Exercise & Hormones for further details and for recommended supplements for IR.
  2. Discontinue all glucosamine and chondroitin products. These nutraceuticals are concentrated sugars which block the beta cells of the pancreas from producing adequate levels of insulin which can cause weight gain and higher blood sugar levels. Glucosamine products can also cause heart irregularities.
  3. Use these highly recommended Nutrients and Herbal Blends.
Vitamin B6 – 1 tsp daily (= 750 mg)

Supports hormone production, pituitary function, and insulin production.

Magnesium Citrate – 1 Tbsp daily (= 1,500 mg)

Natural relaxant, supports normal sugar metabolism, stress and nerve nutrient.

Hormone Boost herbal blend – ¼ cup daily
Helps to alleviate symptoms associated with PPID: slow shedding, sweating, curly hair, low energy, and depression.

Performance Plus herbal blend – 2 Tbsp daily
Provides essential fatty acids for hormone production, helps support sugar metabolism; encourages energy, vitality, and a healthy immune system.

What Your Natural Horse Can Expect

With an understanding of the underlying causes of Equine Cushing’s or PPID along with an effective natural health program that is also cost-effective, horses everywhere can expect to feel better and live a healthier lifestyle. By taking a natural approach and supplementing with the well selected remedies above you will be providing your horse with long-term health benefits and a higher quality of life.

If you want to read more about a Cushing’s horse that turned his life around with diet, nutrition and natural medicine, read our blog:  “Zak Overcomes Equine Cushing’s (PPID) on Riva’s Natural Health Program” who was 16 years old when he started to show symptoms of Equine Metabolic Syndrome and Pituitary disfunction.