Cushings (Pars Pituitary Intermedius Disorder ((PPID)) and Equine Metabolic Syndrome (EMS) are the two most common metabolic/hormone disorders of the horse and pony. In general, Cushings affects older horses, whereas EMS first develops in young and middle-aged animals. Although they are two separate conditions, they can overlap. All breeds are susceptible but ponies are most at risk.
This is due to a dysfunction in a small area of the horse’s brain and it disrupts the normal balance of hormones, mainly affecting ACTH and cortisol (stress hormones). The most common sign are your horse developing a long, thick, curly coat or not losing his/her winter coat. Other early signs of Cushings are vague but include; reduced performance, lethargy and regional fat deposits (bulging supraorbital fat pads, shoulder fat pads, “cresty neck” and fat accumulation around their tail base). The more advanced signs of the disease include; muscle wasting, a pendulous abdomen, sway back, increased sweating (linked to not shedding their coat), blindness, recurrent infections (including parasites, skin infections and synovitis), reduced fertility in mares and increase drinking and urination.
The most import aspect of this disease is laminitis; this can feature early on in the disease process and is usually the condition, which leads to diagnosis of Cushing’s. Laminitis is an inflammation and breakdown of the lamellae. The lamellae suspends and supports the pedal bone within the hoof capsule. When these lamellae are disrupted, the pedal bone sinks and rotates which then causes lameness. Cushings causes a break down in the lamellae proteins and reduces lamellae blood flow. This is why horses with Cushings are predisposed to laminitis.
Diagnosis is usually made on history and clinical exam; however, to be sure a blood test is usually conducted. The blood test measures the hormone ACTH as horses and ponies with Cushings have significantly higher levels of ACTH. It is not 100% diagnostic and may miss early cases but will confirm most and gives you the ability to measure the success of treatment. The hormone ACTH usually peaks in the autumn naturally and so this is the best time of year to test horses suspected of having Cushings. When determining baseline ACTH concentrations it is important to consider that stress may increase ACTH levels so the horse must first recover any bouts of stress or laminitis. Other tests are available if the result of this test does not match with the clinical picture of the horse.
Cushings is a condition mainly of older horses and so management is vital, including; feeding high-quality foods, regular dental care, deworming, and farrier care. Management and treatment depends on severity of condition, if the horse has a hairy coat then you can manage them simply with regular clipping. However, if the horse or pony is suffering from laminitis then management and pharmacological intervention will be required.
Pergolide ‘Pracend’ is the first-line treatment of horses and ponies with Cushings, it is a lifelong treatment that needs to be coupled with management changes. Once a treatment has been started, if there are no signs of improvement after 4 to 6 weeks, the dose should be increased gradually every 3 to 4 weeks. Treatment should be monitored by assessing both improvement of clinical signs and repeat blood tests to check for normalisation of ACTH concentrations. Most horses show improvement within 6 to 8 weeks of treatment. Within a month you can expect to see an improved attitude and reduced lethargy, however improvements in coat, muscle mass and laminitis may take up to a year. This is a lifelong management that needs to include laminitis management as well.
This occurs because fat tissue is active and produces its own hormones. These hormones reduce your horse’s response to insulin, making your horse insulin resistant (IR) this leads to a high concentration of both insulin and glucose in your horse’s blood stream (it also increases the level of cortisol, like in Cushings). This condition in very basic terms can be considered “Horse Diabetes” with a bit of Cushings. These horses are usually obese or “good doers” however, some horses can be lean but still have EMS.
EMS is characterised by obesity or regional adiposity, insulin resistance (IR), and subclinical or clinical laminitis. Laminitis is the most important component of EMS; this condition is most difficult to manage. IR predisposes a horse to laminitis by; altering blood flow and reducing nutrient delivery to the hoof tissues and generating inflammatory or oxidative damage. EMS horses therefore cannot tolerate normal laminitis triggers such as; grass rich in sugars and starches, grazing on abundant and rapidly growing grass, grazing after a frost or in periods of cold night and warm days (this changes the sugars within the grass and they become more readily available).
Diagnosis is made on clinical examination and history but there are blood tests that can confirm the diagnosis and again it is good to have a base line from which to judge the success of treatment. To diagnose EMS in horses, insulin and glucose concentrations can be measured in a blood test. Horses are starved for 6 hours over night and a blood test taken in the morning. Stress raises insulin concentrations in horses so it is important not to take a blood sample whilst the horse is suffering from laminitis. Another test available is an Oral Glucose Test, the horse is starved overnight for 6 hours then a blood sample is taken in the morning before giving a high glucose feed (1g/kg) in a very small feed. After this, blood samples are collected 2 and 4 hours later.
Management of IR/EMS involves mainly weight loss and laminitis management. This can be achieved by reducing sugar and starch intake, soaking hay, removing fat supplements, restricting turnout and regular daily light exercise. Exercise when the horse is sound is essential as it can decreases IR. Leaner horses with EMS are challenging to manage from a dietary standpoint because more calories must be provided without exacerbating IR. Most horses or ponies with EMS can be effectively managed by controlling the diet and reducing body fat, however, it takes time for these management changes to take effect, so drugs such as Metformin can aid the process and accelerate the improvement if the patient suffers from recurrent laminitis.
For both these conditions, the horse needs to be treated as an individual so close work with your vet and farrier is essential in successful management. If you have any concerns, your horse or pony may be suffering from Cushings or EMS then contact your vet for a consultation.