Equine pituitary pars intermedia dysfunction (PPID) is a malfunction of the pituitary gland causing reduced dopamine production and uncontrolled hormone secretion, resulting in symptoms such as abnormal hair, sweating, and susceptibility to infections. Pergolide is the most significant treatment, while natural options include magnesium supplementation and herbal medicines. Management measures include a low carbohydrate/high fat diet, pest control, and regular veterinary check-ups. PPID horses have a better prognosis than ever before with proper treatment and management.
Equine pituitary pars intermedia dysfunction (PPID) was first identified in the 1930s as equine Cushing’s disease. At the time, it was considered a rare complication of old age in horses. It was renamed PPID in the late 1990s when researchers recognized the variations in the disorder between horses versus people and dogs.
PPID is a malfunction of the pituitary gland, resulting from a tumor or enlargement of the gland, putting pressure on the hypothalamus. This, in turn, causes a reduced production of dopamine. Without naturally regulated levels of dopamine, pituitary cells secrete uncontrolled amounts of hormones, including high levels of the steroid cortisol. Increased cortisol levels result in a depressed immune system causing varying degrees of symptoms.
The most common symptom of PPID is hirsutism (abnormal hair). A shaggy, long, thick, often curly coat is often preceded by years of subtle variations in the coat. Hyperhidrosis (sweating) leads to discomfort and health complications, especially in the winter months in cold regions. Other common clinical signs and symptoms include increased susceptibility to internal parasitic invasions, sinusitis, sole abscesses, muscle wasting, extreme thirst, frequent urination, periodontal disease, skin infections, swayback, pot bump, laminitis, and pneumonia.
The average age at which horses contract PPID is 20 years, with 85% over the age of 15 at diagnosis. Although ponies over the age of 15 have a very high incidence of the disease, there is no apparent gender or breed predisposition in horses. The veterinary community is seeing a large increase in reported PPID cases, primarily due to horses’ unprecedented longevity, which is now possible through advanced medical care, parasite control, and nutrition.
The pharmaceutical treatment options available for PPID actually target the source of the problem. The most significant treatment is the use of pergolide, a dopaminergic therapy. This drug is also used in human patients with Parkinson’s disease. In humans, the patient eventually becomes resistant to pergolide, but in horses, there are no signs of resistance development. The low dosage required for horses is suspected to be minimizing this effect. The serotonin blocker cyproheptadine is another option, although there is inconsistent evidence of a therapeutic benefit of this drug.
Natural options include magnesium supplementation, acupuncture, homeopathy and herbal medicines. While some have found success with natural adjustments, it takes a very intense regimen to find a balance that makes your horse comfortable. Meanwhile, he is prone to a number of conditions of which infections and laminitis are the main concern.
Management measures include diet, antioxidant supplements, pest control, dental care, farriery and body trimming. As with insulin resistant horses, a low carbohydrate/high fat diet is recommended. Limit your horse’s access to lush pastures. Grass hays are a safer option than legumes (clover, alfalfa) because they contain fewer carbohydrates.
Extensive testing for PPID includes a complete blood count (CBC), clinical chemistry panel, and urinalysis; followed by a two-day PPID-specific test. PPID horses have a better prognosis than ever before. With proper treatment and management, they can enjoy a long and productive life.
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