Equine Cushings Disease
Kate Hore RNutr(Animal). Snr Nutritionist at NAF
PPID or Cushings disease affects as many as 30% of the older horse population, making it very common and as awareness increases more cases are diagnosed; what was once just a sign of getting older, is now often recognised as a symptom of Cushings. Excessive sweating, long curly coats which are difficult to shed, excessive drinking and subsequent frequent urination are all now recognised signs of PPID in horses. But what really is going on with Cushings?
The pituitary gland sits at the base of the brain, and it is damage to this tiny area, that exerts such effects throughout the horse or ponies body. Whilst a healthy pituitary gland will allow the release and inhibition of hormones, in horses with PPID, the inhibitory processes are reduced due to nerve damage, causing excessive levels of hormones to be released within the body. Hormones control the desire for food and water, the shedding of the coat and even muscle health, so when these become unbalanced we see considerable changes in the normal body functions of our horses. Ponies are more commonly affected than horses, though there has not yet been any breed or sex bias found.
Laminitis is one of the best known signs, though may not always be attributed to Cushings initially. Sometimes we see horses who will have repeated bouts of laminitis, with no real cause or trigger to be found, if this is the case, particularly if the horse is older, then Cushings should be looked at as a potential contributing factor. Alongside the Laminitis may be abnormal fat distribution, resulting in pads of fat or neck crests, even on restricted diets, the supra-orbital cavity above the eye is often noted, as this begins to bulge due to fat deposition, making them appear frog eyed. In other areas you may see muscle wastage or a potbellied appearance; recurrent infections, skin issues, or parasite problems are also typical with PPID and demonstrate the effects of a compromised immune system.
Diagnosis by your vet will be based on a number of factors, including your horse’s clinical history but also using blood tests to ascertain the levels of hormones within the blood. The TRH test looks at levels of ACTH ( adrenocorticotrophic hormone), though frequently used, it isn’t always reliable, particularly as hormonal output varies according to season, and the fact that many tests will produce false negatives when the disease is in its earliest stages. When used in combination with clinical observations and reports from owners, these blood tests can help to diagnose your horses problem. The most common medication used to manage PPID, as we are currently unable to cure the condition, is Prascend or as some will know it, Pergolide. This will help to deal with the hormonal imbalance, though it is not without side effects. It can often take a while to find the correct dose for your horse, so don’t be dis heartened if you don’t see instant results. Some owner will choose to avoid the medicinal route and see if they are able to manage the condition themselves, which for cases in the earlier stages can be done, though always make sure you work in conjunction with your vet to discuss all potential paths and outcomes for you all.