The endocrine system encompasses the pituitary gland and hypothalamus within the brain and the adrenal glands. It is a very important system required for the production of hormones necessary for growth and development throughout life.
There are two main endocrine diseases that commonly occur in the horse, Equine Metabolic Syndrome (EMS) and Cushing's Disease. Both of these can result in laminitis; however, there are distinct differences between the two syndromes.
EQUINE METABOLIC SYNDROME (EMS)
EMS goes hand in hand with the increasing levels of obesity found amongst the equine population, although fat animals do not necessarily have EMS; and EMS may be present in horses and ponies of normal weight. Although previous history of the affected horse or pony may be unknown, it is likely that normally weighted animals with EMS will have been obese at some point in their past. Historically it was thought ponies, especially native breeds were more susceptible to developing EMS and weight gain, but it is possible in any animal.
In susceptible animals, fat tends to be distributed at the crest, around the shoulders and across the rump and buttocks. In addition to this there is often a lot of internal fat as well. This fat is metabolically active and produces a lot of inflammatory proteins which can result in many problems. In humans, metabolic syndrome is associated with increased risk of heart disease and arthritis. Over time, the presence of fat can lead to the pony being resistant to the insulin it produces, this in turn leads to the pony producing more insulin.
The laminitis is a direct result of the high circulating insulin, rather than high glucose levels, and when this resolves, so should the laminitis. The treatment is two–fold; initially dealing with the laminitis and addressing the underlying EMS. Horses and ponies suffering with EMS will go onto a low sugar, low calorie diet that will be tailor made depending on their weight and requirements.
If you have any concerns about your animal’s weight or want to discuss EMS please contact us to have a chat about it. In addition, please do not forget we have a weigh bridge that is free to use, just ring to let us know you are coming!
Cushing’s disease, more correctly known as Pituitary Pars Intermedia Dysfunction (PPID) is the result of a specific nerve cell loss, resulting in hormone disturbances from overdevelopment of the pituitary gland within the brain. This condition is very common in older horses; affecting around 85% of veterans, although it is increasingly diagnosed in younger animals. The main clinical signs include:
- poor performance
- muscle loss
- curly coat
- pot belly appearance
- pottery gait, more severe, or refractory laminitis
The pituitary enlargement is very slow and its presence in the brain usually has no clinical signs; however exceptionally rarely it can be associated with neurological signs, for example, behavioural changes, seizures or blindness.
PPID can be easily diagnosed by a blood test measuring a hormone called ACTH, either at rest or following stimulation. If the tests are positive we advise treatment with pergolide (Prascend), a tablet which controls the levels of hormones produced and can improve the clinical signs dramatically. We usually recommend a repeat blood test in 4-6 weeks to check to dose is correct. Horses and ponies with controlled PPID have a much improved quality of life, and treatment can increase survival by up to 5 years.