Keeping you informed: PPID (Cushing’s Disease) and EMS

What are PPID and EMS?

Pituitary Pars Intermedia Dysfunction (PPID) (commonly known as Cushing’s disease) and Equine Metabolic Syndrome (EMS). These are both examples of endocrine (hormone) diseases, caused by imbalances in the horse’s hormones. Hormones control the body by telling it what chemicals to produce, and imbalances cause the production of too much of some chemicals leading to symptoms. PPID and EMS are the most common endocrine diseases in horses, but other examples include diabetes, thyroid gland disorders and adrenocortical dysfunction, though these are far less common.

PPID

As the name suggests, PPID involves dysfunction of the pituitary gland, specifically the pars intermedia lobe. Dysfunction in this lobe causes excess production of pituitary hormones which then enter the blood stream and affect the whole horse. Clinical signs include: hirsutism (long curly coat with delayed shedding), lethargy, abnormal fat deposits, laminitis, excess thirst and urination, weight loss, immune compromise and loss of topline, ‘pot-belly’. PPID is very common, with some studies suggesting up to 25% of horses over the age of 15 have PPID.

EMS

Equine Metabolic Syndrome can be thought of as similar to diabetes in humans. The main component is an inability to regulate insulin levels in the blood, commonly called insulin dysregulation. The other components are an increased risk of laminitis, and obesity and/or regional abnormal fat deposits (adiposity). Clinical signs include: obesity, difficulty losing weight, recurrent laminitis, increased thirst and urination, adiposity, infertility, lethargy. This is a very common disease, particularly in native horse and pony breeds.

Why are these diseases a problem?

Endocrine diseases are problematic because they have widespread impacts on the whole body. Laminitis is a common clinical sign (see Laminitis information sheet for more details) which can have long term implications. As such, the sooner we can identify and treat endocrine diseases, the better.

How can we make a diagnosis?

Most endocrine diseases are diagnosed by clinical signs and history in combination with blood testing. This is a common and simple procedure which allows us to get a numerical value that we can use to make a definitive diagnosis and track your horses progress. Results can usually be obtained within a few days. In some circumstances, if we have a very high index of clinical suspicion and the case calls for it (for example acute and severe laminitis), we may begin to treat presumptively while we wait for the results. If results are inconclusive, meaning that we cannot rule in or out a disease, we may do follow up testing which we would be happy to explain in more detail in person or over the phone. It is not uncommon to have false positive or negative results so we always consider the full picture before making a diagnosis.

How can we manage them?

Luckily, we have access to safe and effective drugs for treating most endocrine disorders. Alongside careful management this allows us to give horses a good quality of life.

PPID

In the UK, pergolide is the most common medication used. Pergolide is a dopamine agonist and works by regulating the production of hormones from the pituitary gland. There may be some dose changes needed to find the correct dose for your horse. As there are some possible side effects we will always start with a low dose, then repeat testing to check this is controlling your horses clinical signs. For the large majority of horses this is a safe and simple way to treat the disease and give the best quality of life. Other treatment involves treating any clinical signs that are present e.g. laminitis, secondary infections, diet changes.

EMS

There are two main approaches to treating EMS – management and medication. Historically the drug of choice was metformin. Metformin’s effects in horses are not fully understood but it is thought that it works by helping muscle cells absorb glucose without insulin and reducing the amount of glucose absorbed from the intestines. In clinical use, metformin is effective for some horses but works less well for others. In the past few years, a new drug has been licensed for the treatment of EMS in horses called ertugliflozin. While this is a new product to the veterinary market it has been rolled out in large numbers to good effect. Ertugliflozin works by increasing the excretion of glucose through urine, as such it can cause excessive urination and thirst as a side effect. However, the long-term cornerstone treatment of EMS is weight control and exercise. If your horse has active laminitis then exercise should wait until your vet has cleared you, but after that a controlled exercise programme tailored to your horses fitness, age etc will be greatly beneficial. Weight control can also be achieved by dietary changes. This usually means giving a low-calorie balancer and soaked hay. However the exact diet will depend on various factors so it is important to obtain advice from your vet, and nutritionist if you have one.

If you have any questions surrounding PPID or EMS, get in touch with our team on office@starlingequinevets.co.uk or 01473 970393.