Equine Cushing’s disease, more accurately called pituitary pars intermedia dysfunction (PPID), impacts the pituitary gland and results in excessive hormone production. Although many people refer to it as Cushing’s, horses don’t get the same disease as people do. Cushing’s in humans involves increased cortisol, but this isn’t usually the case with horses.
PPID primarily affects horses over the age of 10, with the average age of diagnosis being around 19. Diagnosing Cushing’s horses can be tricky because the symptoms develop slowly, and other health issues can complicate matters. However, proper management can help keep your horse comfortable and healthy.
What causes PPID?
To understand PPID, it helps to know a little about the pituitary gland. The pituitary gland is a small structure at the base of the brain that regulates a lot of bodily functions by releasing hormones into the bloodstream.
The pars intermedia is a specific part of the pituitary gland, and it’s the part that’s affected in horses with PPID.
PPID is caused by the degeneration of neurons, which are brain cells that release dopamine. Dopamine normally keeps the pars intermedia in check, but when those dopamine-releasing neurons start to die off, the pars intermedia goes into overdrive and starts churning out too many hormones, including adrenocorticotropic hormone (ACTH).
What are the signs of Cushing’s in horses?
Cushing’s, or PPID, can cause a wide range of symptoms in horses, and not every horse will show every sign. The severity of the symptoms can also vary quite a bit from horse to horse. However, some of the more common signs include:
- A long coat that doesn’t shed properly (hirsutism)
- Laminitis
- Lethargy and a decline in performance
- Excessive sweating
- Weight loss or muscle loss
- Drinking and urinating more than normal (polydipsia/polyuria)
Horses with PPID are also more prone to infections and may heal slowly from wounds.
How is PPID diagnosed?
Diagnosing PPID in horses can be tricky, because the symptoms develop slowly, and hormone levels can fluctuate, leading to false negatives on diagnostic tests. Plus, there’s no single test that will give you a definitive answer.
Diagnostic tests
Two of the most common tests are:
- ACTH test. This test measures the baseline or basal concentration of adrenocorticotropic hormone (ACTH) in the horse’s blood.
- TRH stimulation test. In this test, the veterinarian measures ACTH levels after giving the horse an injection of thyrotropin-releasing hormone (TRH).
Factors affecting diagnosis
Seasonal changes can cause hormone levels to go up and down, so it’s important to work closely with your veterinarian to interpret test results and decide on the best course of action for your horse.
Treatment and Management Strategies
Treatment for equine Cushing’s disease focuses on controlling symptoms and improving the horse’s quality of life.
Pharmaceutical Treatment
Dopamine agonists, especially pergolide, are often prescribed. Pergolide helps regulate hormone production and is effective in a majority of cases, improving symptoms in 65% to 85% of treated horses.
Like any medication, pergolide can have side effects, including reduced appetite and lethargy.
Management and Supportive Care
In some instances, managing the clinical signs of Cushing’s may be enough to keep your horse comfortable and healthy.
Dietary adjustments can also help, especially low-starch and low-sugar diets, which can help to manage insulin resistance and the risk of laminitis.
Regular farrier care is also important, because regular trimming and shoeing are crucial for horses who are experiencing laminitis.
To Conclude
If you think your horse might have PPID, it’s vital to seek a diagnosis and begin treatment as soon as possible. Early detection and careful management are key to improving your horse’s quality of life.
Management strategies often involve medication, changes to your horse’s diet, and attentive hoof care.
Finally, remember that Cushing’s is a progressive disease, so ongoing monitoring is essential. Make sure your horse has regular checkups with your veterinarian so that the treatment plan can be adjusted as needed to ensure your horse’s comfort and well-being.