{"id":38744,"date":"2014-07-28T23:23:38","date_gmt":"2014-07-28T23:23:38","guid":{"rendered":"https:\/\/horseandcountry.tv\/vet-essentials-equine-cushings\/"},"modified":"2023-06-07T17:37:24","modified_gmt":"2023-06-07T16:37:24","slug":"vet-essentials-equine-cushings","status":"publish","type":"post","link":"https:\/\/press.horseandcountry.tv\/en-us\/vet-essentials-equine-cushings\/","title":{"rendered":"Vet Essentials: All about Equine Cushing’s"},"content":{"rendered":"

Our series Vet Essentials<\/a> takes a look at some of the common health issues affecting horses. In this article, veterinary surgeon\u00a0<\/strong>David Rendle takes a look at Equine Cushing\u2019s Disease – also known as PPID.\u00a0<\/strong><\/p>\n

Equine Cushing\u2019s Disease is frequently cited as being the most common hormonal disease of horses. More correctly, the disease should be called Pituitary Pars Intermedia Dysfunction (PPID) because it is now known that the disease in horses is different from human Cushing\u2019s disease, a pituitary condition named after an eminent human neurosurgeon Harvey Cushing.<\/p>\n

Why does it occur?<\/strong><\/h2>\n

The disease develops when nerve fibres within the brain become damaged. The nerve fibres that are most susceptible to damage run from an area of the brain called the hypothalamus to a gland at the base of the brain called the pituitary gland, and would normally cause a substance called dopamine to be released into the pituitary. Dopamine acts as an \u201coff signal\u201d, inhibiting the production of many hormones from the pituitary gland.<\/p>\n

When the nerve supply to the pituitary gland becomes damaged there is less control over a part of the pituitary gland called the \u201cPars Intermedia<\/em>\u201d and increased quantities of certain hormones are released from this structure \u2013 hence the term \u201cPituitary Pars Intermedia Dysfunction\u201d or PPID. The exact reasons why this nerve damage occurs are not known but it is clear that the damage becomes worse as horses get older. It has been suggested that horses and ponies that are obese may be more susceptible to this damage, and although there are logical reasons why this might be so, it has certainly not been proven. This suggestion does however provide a further reason, should one be needed, to tackle the UK\u2019s equine obesity epidemic.<\/p>\n

Which horses are affected?<\/h2>\n

We used to consider that equine Cushing\u2019s was a disease of older horses, however research now indicates that the damage to the nerve fibres can begin quite early in life, frequently in the early teens and even younger. Two separate studies, one performed in Australia and one in the UK, have demonstrated that one in five horses over the age of 15 are likely have PPID and once horses or ponies reach their late twenties the majority are likely to have the disease.<\/p>\n

What are the symptoms?<\/h2>\n

We are all aware that horses with Cushing\u2019s develop excessive hair growth or retain their hair coat for longer after the winter. This condition is known as \u201chirsutism\u201d or \u201chypertrichosis\u201d and tends to affect horses with advanced Cushing\u2019s disease. Unfortunately many of the earlier signs of Cushing\u2019s that may affect horses in their teens or even younger are non-specific and easily missed.<\/p>\n

Studies have shown that owners of ageing horses struggle to recognise the signs of Cushing\u2019s. It may be that they are unaware of many of the early signs but also because it is difficult to notice the very gradual changes in their horse\u2019s appearance and demeanour. Often these subtle changes are accepted as being part of the normal ageing process \u00a0when in fact, if due to Cushing\u2019s, \u00a0could be partially reversible. Often these clinical signs are only appreciated as they disappear after the horse receives medical treatment.<\/p>\n

Although many of the changes that occur in horses with Cushing\u2019s are of relatively minor importance to the animal\u2019s well-being, the major concern is laminitis<\/a>. A recent study showed that horses with Cushing\u2019s were four- to five-times more likely to suffer from laminitis. This risk may be higher in the autumn when hormone levels in Cushing\u2019s cases get even higher.<\/p>\n

Alarmingly, the first sign of Cushing\u2019s disease may be the development of laminitis. This was highlighted recently by the loss of the Australian Olympic Dressage hopeful Victory Salute who developed laminitis at the age of 11 and was subsequently diagnosed with Cushing\u2019s disease. Recent research has shown that around a third of laminitis cases have underlying Cushing\u2019s and in one investigation performed in the United States the figure was 70%. In a study performed by The Liphook Equine Hospital in Hampshire looking at the situation in the UK, blood samples from laminitic horses tested by vets across the country were reviewed and it was found that 36% of laminitis cases had Cushing\u2019s disease.<\/p>\n

It is therefore very important that all but the youngest horses with laminitis are tested for Cushing\u2019s disease. The percentage of laminitic horses and ponies suspected of having Cushing\u2019s and subsequently testing positive is shown in the graph in figure 1; demonstrating that although the chance of an animal having Cushing\u2019s as it gets older is heightened, younger animals should not be discounted. If Cushing\u2019s is contributing towards the development of laminitis then the laminitis will not be controlled effectively without treatment of the underlying Cushing\u2019s disease.<\/p>\n

Other clinical signs of Cushing\u2019s that are often more difficult to identify include:<\/p>\n