How Does Cushing’s Disease Start?

Cushing’s Disease is also known as Pituitary Pars Intermedia Dysfunction (PPID) because it involves both the hypothalamus and the pituitary gland. However, I prefer to avoid the term PPID which focuses on the pituitary gland as the primary cause, which, is not exactly the case; PPID, like almost all other diseases, develop from a myriad of different factors that affect other organs as well. And most of those factors are caused by a domestic lifestyle.

The pituitary is a tiny little gland (its size belies its importance) located at the base of the brain behind the sphenoid sinus cavity. It’s about the size of a grape. Its job is to produce specific hormones in response to signals from the hypothalamus. The hypothalamus is another slightly larger gland just above the pituitary and is attached to it by a stalk.

The hypothalamus responds to a variety of internal and external signals to maintain homeostasis (balance) by stimulating the pituitary to produce important hormones. The hypothalamus is the major integrating link between the nervous system and the endocrine system. Therefore, body temperature, hunger, satiety, various emotions, motivation, pain, and stress, all have an effect on hormone production.

Instructed by the hypothalamus, the pituitary then regulates all other endocrine glands by releasing hormones directly into the blood stream to communicate with the thyroid, adrenal glands, thymus, ovaries, testicles, and the islets of Langerhans cells in the pancreas that produce insulin. It’s a sophisticated and incredibly complex system, that when healthy, serves the body well.

But in Cushing’s Disease, the pathways between the hypothalamus, the pituitary, and the adrenal glands are disrupted because the hypothalamus signals the pituitary to produce too much adrenocorticotropic hormone (ACTH) which causes the adrenal glands to produce an excess of cortisol. 

Why is Cortisol a Problem?

At normal levels, cortisol is an important part of the horse’s overall health. It helps a horse cope with stress, control inflammation, and regulate the immune system. Cortisol is a natural anti-inflammatory which is produced during any kind of physical pain or discomfort.

But the problem with cortisol begins when the levels don’t drop back down to normal as is often the case with our stressed-out domestic horses. The life of a domestic horse is not easy; most of them are caught up in a cycle of constant stress caused by high sugar diets, grass pastures, isolation, confinement, pain, inflammation, over-medicating, over-training, lack of exercise, abuse, and neglect. In states of chronic and prolonged stress, cortisol levels remain high for long periods of time. And it is these high levels of cortisol which starts the freight train of damage.

Aside from the effects of cortisol on the brain, it results in weight gain, insulin dysregulation, thyroid imbalances, tissue breakdown (catabolism) including hoof tissue, laminitis, a depressed immune system, muscle wasting, bone and joint weakness, and depression and anxiety.

The Dopamine Connection

Newer research has discovered that the disruption between the hypothalamus-pituitary pathway is actually because of a dopamine deficiency. Dopamine is a neurotransmitter that helps to regulate the pars intermedia (middle) portion of the pituitary gland and controls the over-production of its hormones. But some of the neurons (brain cells) which produce dopamine are degenerated and are therefore unable to produce adequate levels to control the pituitary hormones.

These uncontrolled pituitary hormones, including ACTH, run amok affecting other body functions. But aside from the hormone confusion the primary complication is that the pituitary begins to enlarge, and often forms an adenoma, i.e., a benign tumour, which is white to yellow in colour. Pituitary adenomas produce an abnormal production of ACTH (as well as other lesser-known hormones). This pituitary enlargement is thought to be the result of the dopamine deficiency causing the pituitary to secrete large unregulated quantities of ACTH which it is not hardwired to do at those levels. And so, just like any other overworked gland or organ, it begins to enlarge.

Now from a purely science point of view the primary cause of Equine Cushing’s disease is thought to be these damaged neurons that can no longer produce enough dopamine. But the mystery of why the dopamine neurons have been damaged in the first place has not been solved. At least not in the lab.

In the holistic model, however, we always look for the true and underlying cause of the imbalance rather than focussing just on the mechanics of the condition. Following the chemical trail often leads to a dead-end unless the objective is to design a new pharmaceutical.

And so, we must ask, how is it logically possible that so many senior horses have a pituitary tumour? This is beyond random. And why don’t as many horses also have skin cancer, a kidney tumour, or a muscle disease, or whatever…Why is it specifically a dopamine-ACTH problem? And what other purposes does dopamine have that the levels need to be so high that it burns out the neurons? Let’s see if we can connect the dots.

The Dopamine Lifestyle

Dopamine is a type of neurotransmitter that sends important signals from the brain to the body. It is important for motor skills, cognitive abilities, memory, and learning new things. It helps with focus and attention span and affects sleep patterns and social behaviours. It also plays a key role in the reward and motivation system by producing feelings of pleasure, as well as excitement like when something important is about to happen! Rewards resulting in pleasure is significant for horses since the biggest reward for a horse is sugar! Just like people.

Low levels of dopamine are known to cause lethargy, muscle stiffness, fatigue, apathy, and depression, all of which we so often see in our Cushing’s horses. A dopamine deficiency can also cause attention deficit, digestive problems, and weight gain.

But what’s really important regarding our horses is that dopamine production is affected by quality of sleep, excess weight or obesity, lack of exercise, and a probiotic deficiency which affects the hindgut microbiome. And stress is by far the biggest component; horses are adversely affected by confinement, isolation, boredom, over-training, herd dynamics, emotional problems, and of course diet and nutrition. Even weather extremes, especially cold and hot temperatures, can cause them enough stress to alter hormone levels.

Cushing’s Disease has everything to do with lifestyle, and the stressors of domestic living. Why else would it be an epidemic?

Conventional Treatment for Equine Cushing’s

The current medications for PPID act as a dopamine substitute to encourage the pituitary to suppress its hormone production. These medications do not however, extend longevity and some experts question how many horses actually improve their quality of life. Some horses seem to tolerate it, but we do know that the medications can cause multiple side effects including decreased appetite or anorexia, diarrhea, colic, fatigue, weight loss, skin problems, joint or muscle pain, and a fast heartbeat. Depression, anxiety, and behavioural changes are also common. Similar medications intended for people were removed from the U.S. market several years ago due to serious side-effects and safety concerns. Go natural…

Natural Health Program for Cushing’s Disease (PPID)

The majority, if not all, Cushing’s horses either have IR or some degree of sugar sensitivity/metabolic disorder. Therefore, diet, nutrition, exercise, and the reduction of stress levels are key

And some of these horses, even though they have high ACTH levels, do not technically have PPID. Yet. So, there is lots of time to “catch” these horses by addressing the underlying imbalances before the condition becomes more advanced.

Herbal remedies and homeopathy complete the program.

Cushings Disease (PPID) Bundle Special:

HPA Balance herbal blend –Promotes a healthy endocrine system including the adrenal, thyroid, and pituitary glands. Maintains hormone balance.

Vitamin B6 - Nutritional support for hormone production, as well as thyroid and pituitary function. Supports mental health and energy levels.

Vitex Plus homeopathic remedy – Maintains normal hair growth, shedding, body temperature, and energy levels. Supports normal pituitary function.

Pro-Colon probiotics – ¼ tsp daily

A balanced microbiome is proven to be very important for a variety of health conditions and hormone imbalances. A healthy microbiome supports the intestinal immune system, maintains digestion and nutrient absorption, and aids leaky gut. 

Metabolism Drops, homeopathic – One dose (5-10 sprays) daily for 21 days or longer as needed.

This remedy is best used if the Cushing’s horse is overweight or has an excessive appetite. Supports normal blood sugar levels, maintains normal body weight, and normalizes appetite in overweight horses.

Vitamin B6 – 750 mg daily (= 1 tsp)

Nutritional support for hormone production, as well as thyroid and pituitary function. Supports mental health and energy levels.

HPA Balance herbal blend – 2-3 Tbsp daily

An herbal blend containing a proprietary blend of Ashwaghanda, Licorice Root, Chaste Berry, Kelp, and Raspberry Leaf to support horses with hormone imbalances. Promotes healthy adrenal and pituitary function. Maintains calm behaviour.

Performance Plus herbal blend – 2-3 Tbsp daily.

All all-natural blend of adaptogen herbs to maintain energy levels and vitality. Supports the endocrine system. Promotes hoof growth, normal metabolism, and a healthy immune system. Maintains a healthy nervous system. Chia seeds, Ashwaghanda, Siberian ginseng, and Spirulina. 

Vitex+Plus, homeopathic – One dose (5-10 sprays) daily

A proprietary formula containing homeopathic ACTH, Quercus Robar, and Chaste Berry. Promotes normal hair growth, shedding, body temperature, and energy levels. Supports pituitary health. 

Slow Feeders mimic natural grazing, help to regulate appetite, encourage weight loss, reduce stress, alleviate boredom, and contribute to general health and wellness.