Equine Cushing's disease, also known as PPID, is thought to affect 20% of horses over the age of 15, and is the 5th most common disease syndrome recognised in horses and ponies in the UK*.
This is a significant development from the situation a few years ago where Equine Cushing's disease was considered a rare hormonal disease and frequently remained undiagnosed and uncontrolled
Equine Cushing’s disease is a progressive condition associated with a number of symptoms that can adversely affect the quality of life of your horse. So whilst the initial signs that your horse may present, for example mild coat changes, might not be of significant concern, it’s likely that over time the disease will progress and more severe symptoms will develop that may have a more severe effect on their quality of life. For example laminitis, recurrent infections and lethargy are all more advanced signs of Cushing’s disease. Early recognition and diagnosis provides you with more options to implement management and treatment strategies to keep your horse happy and healthy for as long as possible.
Is it Equine Cushing’s disease or PPID?
The correct veterinary term for the disease is PPID (Pituitary Pars Intermedia Dysfunction). PPID is a more accurate description because it describes the part of the brain affected by the condition. The more commonly used term ‘Cushing’s disease’ originates from the American doctor, Harvey Cushing, who described a different disease in people. Although the human disease also originates in the pituitary gland, it is from a part called the pars anterior, and therefore is a different disease to that which we see in horses. We will use the more familiar ‘Equine Cushing’s disease’ throughout this website, however it is useful to know that PPID is exactly the same disease if you see references to it elsewhere, or on some of the links associated with this website.
*Prevalence, risk factors and clinical signs predictive for equine pituitary pars intermedia dysfunction in aged horses: Prevalence and risk factors for equine PPID MCGOWAN, T. W. , PINCHBECK, G. P. , and MCGOWAN, C. M. Equine Veterinary Journal (volume 45 issue 1 pages 74-79 ) January 2013
What is it?
Equine Cushing’s disease (Cushing’s disease) is a hormonal disease caused by changes in the pituitary gland, which is located at the base of the brain. This gland is normally controlled by a substance called dopamine and its role is to produce a variety of hormones which play an important role in maintaining and controlling a variety of bodily functions. Horses and ponies with Cushing’s don’t produce enough dopamine which means that the pituitary gland becomes uncontrolled and produces too many hormones. One of these hormones is called ACTH*, but it is likely that there are many others.
Watch this video to see what happens to the pituitary gland when a horse develops Cushing’s disease.
The clinical signs of Cushing’s disease are likely to be associated with these elevated hormone levels but the exact link between the elevated hormones and the signs of the disease is still unknown.
*ACTH: Adrenocorticotropic Hormone
Why is it important?
Equine Cushing’s disease is a progressive condition associated with a number of symptoms that can adversely affect the quality of life of your horse. So whilst the initial signs that your horse may present, for example mild coat changes, might not be of significant concern, it’s likely that over time the disease will progress and more severe symptoms will develop that may have a more severe effect on their quality of life. For example laminitis, recurrent infections and lethargy are all more advanced signs of Cushing’s disease.
Early recognition and diagnosis provides you with more options to implement management and treatment strategies to keep your horse happy and healthy for as long as possible.
Which horses are at risk?
Any horse can develop Equine Cushing’s disease, however there are a few factors that can influence the likelihood of developing the condition.
Age: Equine Cushing’s disease is primarily a disease of older horses. There are isolated reports of horses as young as 7 with the disease, but the majority of cases are over 10 years old. One in five horses over 15 will have Cushing’s disease.
Breed Equine Cushing’s disease appears to be more common in native breeds, and less common in thoroughbreds.
What is the link between Equine Cushing’s disease and laminitis?
Equine Cushing’s disease is a common underlying cause of laminitis: in one study up to 70% of horses with laminitis were shown to have high levels of the hormone associated with this condition. The exact link between Cushing’s disease and laminitis is not fully understood, and research into this area is ongoing.
One theory is that Cushing’s disease increases the risk of a horse developing laminitis because most horses with this disease show an exaggerated insulin response (high insulin levels) to food containing sugar (glucose). The theory supposes that when a horse with Cushing’s disease eats grass with a high sugar content, they develop high levels of insulin in their blood, and these high insulin levels cause laminitis. However, the picture is complicated by the fact that not all horses with Cushing’s disease will have insulin resistance, and not all horses with insulin resistance will have Cushing’s disease.
It is thought that in many cases subclinical Cushing’s disease (when the disease is present but there are no obvious clinical signs) will have been present for several months or even years prior to laminitis developing. This means that recognising and treating the disease promptly may reduce the risk of laminitis developing in your horse.
Find out more about how to spot Cushing's disease in your horse.
The treatment for Equine Cushing’s disease is a prescription-only medicine, known as a POM-V, and can only be prescribed by your vet. This section of the website is provided as an information service for owners of horses who have been prescribed the POM-V medicine, Prascend® 1 mg tablets for horses, by their vet. Please click 'OK, I accept' to confirm that you are either a veterinary surgeon or an owner of a horse that has been prescribed Prascend by your vet.
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