Equine Cushing’s Disease

Equine Cushing's Disease is the older name for pituitary pars intermedia dysfunction, a slowly progressive endocrine disorder that affects the pituitary gland at the base of the brain. In affected horses, the pars intermedia portion of the pituitary gland produces excessive amounts of several hormones, including adrenocorticotrophic hormone. This disrupts normal metabolism, immune function, stress responses, coat growth, and body condition. The condition is most common in senior horses, ponies, and donkeys.

Equine Cushing's Disease is caused by changes in the brain and pituitary gland that reduce dopamine control over hormone production. In healthy horses, dopamine helps limit hormone release from the pars intermedia of the pituitary gland. When dopamine-producing neurons degenerate, the pituitary gland can become overactive, enlarge, and produce excessive hormones. Benign tumors may also develop in this part of the gland as the disease progresses.

Signs of Equine Cushing's Disease can include delayed shedding, an abnormally long or curly coat, muscle wasting, loss of topline, lethargy, abnormal sweating, increased thirst, and increased urination. Some horses also develop regional fat deposits, weight loss, infertility, loose teeth, or recurrent infections due to impaired immune function. Laminitis can occur and may be one of the first noticeable signs, especially when hormone levels rise seasonally. Early signs can be subtle, so changes in coat, body condition, performance, or hoof comfort should be discussed with a veterinarian.

Horses with Equine Cushing's Disease have a higher risk of laminitis because the condition is often linked with insulin dysregulation. When insulin levels remain elevated, the sensitive tissues inside the hoof can become damaged and inflamed. Laminitis may appear as hoof heat, a strong digital pulse, a short or stiff gait, shifting weight, reluctance to move, or an abnormal stance. Any suspected laminitis should be treated as urgent and evaluated by a veterinarian.

Equine Cushing's Disease is diagnosed by a veterinarian using blood tests together with the horse's clinical signs. Testing may include measuring adrenocorticotrophic hormone or using other endocrine tests to assess how the pituitary and adrenal systems are functioning. Horses should also be evaluated for insulin dysregulation because this helps determine laminitis risk and feeding management. No single test is perfect, so diagnosis often depends on the full picture of bloodwork, symptoms, age, and response to treatment.

A horse with Equine Cushing's Disease should be managed with veterinary treatment, careful feeding, regular hoof care, dental care, and monitoring of body condition. Horses with heavy coats may need clipping to stay comfortable, especially in warm weather. Exercise can support weight control, insulin sensitivity, and muscle maintenance when the horse is sound and comfortable. Ongoing monitoring is important because feeding needs, medication response, laminitis risk, and body condition can change over time.

Horses with Equine Cushing's Disease should generally be fed a forage-based diet that matches their body condition and insulin status. If insulin dysregulation is present, the diet should be low in simple sugars and starch to help reduce insulin spikes and laminitis risk. Overweight horses may need controlled calorie intake, mature grass hay, restricted pasture access, or a grazing muzzle, while underweight horses may need safe calorie sources that do not worsen insulin regulation. A veterinarian or equine nutritionist can help balance energy, protein, vitamins, and minerals for the individual horse.

Supplements can help support horses with Equine Cushing's Disease when they are used to balance the diet or address specific needs, but they do not replace veterinary treatment. Key nutritional priorities include adequate protein for muscle maintenance, balanced vitamins and minerals, antioxidant support, and nutrients that support glucose metabolism and immune function. Probiotics, prebiotics, yeast, and omega-3 fatty acids may also support gut health, immune function, and inflammatory balance.