What Is Cushing’s Disease In Horses?

Cushing’s disease, also called pituitary pars intermedia dysfunction (PPID), is a hormonal disease affecting horses. It can be scary for horse owners to learn their horse has developed PPID. When left untreated, it can turn fatal.

Fortunately, there are treatment options available to give your horse a comfortable life while battling this incurable disease.

This article will help you to learn more about equine Cushing’s disease, including the causes, symptoms, treatment and prevention.

What Causes Cushing’s Disease?

The brain is a complicated organ. When one part malfunctions, it can cause havoc throughout the body.

Horses (and all mammals) have cells in their brain which produce a substance called dopamine. Dopamine is more than just a feel-good hormone; it also regulates the pituitary gland, which sits at the base of the brain. The purpose of this gland is to produce hormones in response to brain signals.

Cushing’s horses are unable to produce enough dopamine, which causes the pituitary gland to malfunction. This is why the correct medical term for Cushing’s disease is pituitary pars intermedia dysfunction (PPID) – the pars intermedia part of the gland is affected.

The gland enlarges (which can cause tumours), and the production of certain hormones, specifically ACTH (adrenocorticotropic hormone), increases. Other parts of the gland can stop producing hormones or the swelling can apply pressure to the brain, leading to seizures and loss of vision.

ACTH regulates cortisol, which is also known as the stress hormone. When ACTH levels increase unchecked, the symptoms of Cushing’s disease become evident.

An enlarged Pituitary glad (red bulb above) malfunctions leading to the symptoms of cushings

Which Horses and Ponies Get Cushing’s Disease?

PPID is an age-related disease, meaning that it is much more common in older horses than younger ones. It can affect horses and ponies over the age of ten, but most diagnoses are made between the ages of 15 and 19.

Interestingly, ponies are more likely than horses to develop this hormonal disease caused by pituitary gland changes. Mares, geldings and stallions are all equally likely to develop Cushing’s disease.

Symptoms of Cushing’s Disease

Equine Cushing’s disease has a gradual onset. As hormone production is altered, years can pass before the first symptoms start to appear.

Initially, you will spot changes in the horse’s coat. Afflicted horses and ponies grow long, thick or curly coats, even in the height of summer. Ulcers on their hooves as a result of insulin resistance come next. Horses may also develop unusual fat deposits on their body.

These are just the first signs. In the more advanced stages, the following symptoms will persist or occur:

• Winter coat not shedding
• Recurrent infections (skin infections, dental diseases and sinus infections)
• Laminitis
• Muscle atrophy and weight loss
• Wounds not healing
• Kidney dysfunction (drinking more water, urinating frequently)
• Exhaustion or lethargy
• Excessive sweating when not exercising
• Bulging above the eyes
• Hoof ulcers and abscesses

As you can see, equine Cushing’s disease is no joke, and can result in a very painful life for your horse.

A horse not shedding it’s winter coat can indicate Cushings

How to Diagnose Cushing’s Disease

Diagnosis must be done by a vet; even so, it is incredibly difficult due to the nature of the disease.

• PPID has a gradual onset
• Tests can result in false negatives, especially in the early stages
• Hormone levels vary seasonally, affecting test results

Early diagnosis is key, though, as it enables horse owners to manage the disease and keep their animals comfortable.

Vets first consider any clinical signs and the horse’s medical history. Diagnostic tests are then run, using blood samples, to test adrenocorticotropic hormone (ACTH) levels. A thyrotropin-releasing hormone (TRH) stimulation test may also be performed.

It takes a couple of days to get the results.

Treating Cushing’s Disease

Equine Cushing’s disease is incurable – but all hope is not lost. Once diagnosed by taking a blood sample and running the necessary tests, you can treat and manage the disease to keep your horse comfortable.

Once detected, treatment for PPID needs to begin immediately. There are two ways to treat Cushing’s – medical treatment and managing the symptoms.

Medical management

There is medication available that can help to regulate the pituitary gland. Daily medication – a tablet called Prascend hidden in your horse’s food – is usually required.

Prascend increases dopamine production, which means the pituitary gland no longer produces excessive hormones.

Serotonin and cortisol antagonists can also be prescribed to help maintain the pituitary gland’s function.

Medication will be needed for the rest of your horse’s life to manage hormone production.

Symptom management

Apart from medication, you can also manage the symptoms to ensure your horse has a longer, happier life.

Managing symptoms includes:

• Clipping the long or curly coat. This is especially important in summer if the horse does not shed its winter coat.
• Providing the horse with enough healthy fats to prevent laminitis.
• Routinely seeing the equine dentist to check for infections.
• Regular deworming schedule.
• Maintaining your horse’s hooves (a farrier is best suited for this).
• Dietary management – changing up the horse feed to ensure a balanced diet and prevent laminitis.

How to Prevent Cushing’s Disease

Sadly, there isn’t a precise way to prevent Cushing’s disease. However, horse owners can reduce the risk of developing PPID by taking these steps:

• Feed a low-sugar diet
• Regularly test for insulin resistance
• Maintain a healthy body weight
• Exercise your horse regularly
• Routine veterinary appointments (especially if you have a senior horse)

We found the video below a very good resource for understanding the disease.

FAQs

What are the first signs of Cushing’s disease in horses?

The first sign of Cushing’s disease is the development of a long or curly coat that does not shed. The horse may also have unusual fat deposits and loss of muscle on the back and rump (top line). Laminitis may be present, and the horse may have abnormal weight loss.

How long can a horse live with Cushing’s disease?

With veterinary medicine and a healthy lifestyle (exercise and a good, balanced diet), horses can live up to seven years once diagnosed with Cushing’s disease. Sadly it is incurable, but you can ensure your horse is comfortable for the last years of its life.

Can a horse recover completely from Cushing’s disease?

No; horses can’t recover from Cushing’s disease. However, with medication for the clinical signs and management of the symptoms, a horse can still have a good quality of life for several years after diagnosis.