Cushing’s Syndrome is a very common disease of older horses, ponies and donkeys. It is being seen with increasing frequency as horses are living longer, mainly due to better care in old age.
The syndrome is caused by the gradual loss of dopamine, a chemical that sends signals from one part of the brain to another. As the amount of dopamine decreases due to age, the pituitary gland in the brain starts to grow and causes the levels of cortisol in the blood to increase. Cortisol is responsible for regulating many activities within the body, hence the wide range of symptoms seen. The disease is not caused by a tumour, as was previously assumed.
Most horses are in there mid-teens or older when the disease is diagnosed. The most common clinical signs are:
- A long, often curly, coat, especially along the back and lower limbs. In the early stages, it may only be noted that the winter coat fails to shed in the summer.
- Laminitis, which may be fairly mild, but is often resistant to the usual treatments.
- Lethargy, noticed as either becoming easily tired on exercise, or generally very quiet.
- Weight loss over the back and ribs, muscle loss, and pot-bellied appearance.
- Increased sweating.
- Increased susceptibility to infections, including worms, respiratory infections, tooth infections and poor wound healing.
Sometimes the diagnosis can easily be made on examination of the horse alone. In early or less typical cases, though, we may recommend blood testing to confirm the diagnosis. Until 2009 thisinvolved sampling the horse late in the afternoon, giving a small dose of cortoisone by injection at that time, and taking a second sample the following morning. It is thought that the very low dose of cortisone used in this test is highly unlikely to bring on or worsen a case of laminitis. As of 2009 we now recommend a single sample taken for ACTH.
Treatment of Cushing’s Syndrome used to be very expensive and not particularly successful, but medications have become available in the last few years which are very reasonable in price and far more effective. The most useful drug is Pergolide, which increases the amount of dopamine that is produced in the brain and prevents the pituitary gland from stimulating excessive cortisol production. Treatment usually involves giving a tablet, which is readily accepted in the feed by most horses, either daily or every second. Side effects are uncommon and can be prevented by reducing the dose if necessary. If an improvement in the horse’s quality of life is seen, the treatment can be lifelong and may prolong a horse’s life by several years. Other drugs may be used in certain cases. Medication may not be suitable or effective for every affected horse. The dose of Pergolide is usually altered based on repeated ACTH tests.
It is also particularly important with this disease that the management of horse is of a high standard, as affected horses are more susceptible to infections than other horses. Important routine care would include regular worming, dental checks, vaccination and grooming (possibly including clipping of long coats).
If you are concerned that your horse or pony may be suffering from Cushing’s Syndrome, and would like to discuss the options available to you, then please feel free to contact us at Clyde Veterinary Group Equine Hospital, New Lanark Market, Hyndford Road, Lanark, Tel: 01555 660000
The material contained in this website is presented for information purposes only . The material is in no way intended to replace professional veterinary care or attention from a professional veterinary surgeon.
The advice given in any of our web pages cannot be used as the basis for a diagnosis or choice of treatment.
Clyde Vet Group advises that you should always consult a veterinary surgeon about any queries with animals under your care.