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Equine Cushing’s Syndrome

  • Veterinary

(5 April 2013)

Cushing’s syndrome is a common disease in the older horse (above 15 years of age) and it is being diagnosed more and more frequently, since there are more horses living longer.

When we talk about Cushing’s syndrome, we refer to a pathology better defined as Equine Pituitary Pars Intermedia Dysfunction (PPID). The pituitary gland is an endocrine gland located at the base of the brain, and it is part of a complex system of glands and organs and their products, that control many functions of our body.
The Cushing’s dysfunction can be of the Pituitary Gland itself, but it could also originate from a dysfunction of many other parts of this complex system.

The important factor is that the alteration of this balance leads to a chronic increase of the endogenous (produced within the body) glucocorticosteroids (cortisol); these are hormones which have important functions in many parts of the body.
This is the reason why there is such a long list of symptoms associated with Cushing’s Disease in animals.

Often we will only find one, or just a few of these symptoms in one animal; the others might show up in a more advanced stage of the disease, never show up, or be there in a very mild form so that it is not easy to spot them.
As mentioned above, the list of the most common symptoms is quite a long one:
• hirsutism (a long curly coat that does not shed properly): this is the most characteristic symptom of Cushing’s disease);
• chronic laminitis (quite often the only symptom present);
• frequent /recurrent infections due to poor functioning of the immune system (hoof abscesses, tooth root infections, sinusitis etc.) ;
• lethargy, change in behaviour;
• excessive drinking and urination (what the vet calls polyuria/polydipsia); often, if the horse spends some time in the stable, we notice that the floor/bedding gets quite wet;
• redistribution of fat and change in the horse’s ‘shape’, and often weight loss due to muscle loss;
• excessive sweating;
• neurological problems.

Diagnosis is achieved through blood testing but it is not always straightforward.

In some cases, only one blood sample will be sufficient to determine if the horse has PPID; others will need a combination of injections and a few blood samples to achieve a result; other cases again will need more than one test combined to reach a diagnosis. Your vet will offer you the right test for your animal, taking into account the time of year. This is important because there are normal variations in the seasonal activity of the pituary gland that could give you false results, or results that are more difficult to interpret.

The literature mentions different drugs, usually drugs that can help prevent the reduction of cortisol levels. Costs are not prohibitive but it needs to be taken into consideration that a horse on Pergolide (the drug of choice) can cost between€0.50 to €3 per day - and that is for the rest of its life.

There are other things that we can do to improve our Cushing’s horse’s life in addition to the therapy, for example:
• clip the horse in the summer if he doesn’t shed his winter coat (usually they lose it irregularly, resulting in a ‘patchy’ appearance);
• provide him with a very well-balanced diet (talk to your vet about that, don’t improvise);
• check his hooves and mouth frequently and regularly (these are often locations of recurrent infections that otherwise can go undetected for a long time).

It is also quite important to have regular blood tests done in order to monitor your horse and decide if the therapy is adequate for him. It is important to take notes and monitor clinical signs that reflect the evolution of this pathology.
Don’t forget to keep in touch with your veterinarian, reporting every improvement of your horse, or if you think he is getting worse.

This is only a brief explanation and it has been purposely written without scientific terms and references. If you would like to know further details about the disease, please contact the author agnesesanti@email.it

Agnese Santi Med. Vet. MRCVS

In this picture: Miranda, our pony suffering from Cushing’s Syndrome