Cushings Disease

a.k.a. Equine Cushings Disease. PPID (Pituitary Pars Intermedia Dysfunction) is a disorder of the Pituitary Gland located at the base of the brain. The gland produces hormones under neurologic control by the brain. In Cushings Disease either the nerve supply to the gland degenerates or the gland may be affected by a tumor called an adenoma. The amount of Cortisol hormone released into the circulation by the gland increases, affecting the body in several ways. Hair growth is increased (Hirsutism) and shedding of the winter coat is delayed, so these horses tend to look hairy and scruffy. Drinking and urination increase (Polydipsia & Polyuria) as does sweating, and skin infections. The immune system function tends to be depressed and a heavy burden of intestinal parasites may be present and require monitoring and treatment. Body Condition slowly falls away and affected horses loose muscle tone and may appear pot- bellied. They are lethargic and abnormally prone to Laminitis. Usually affecting older horses and ponies over ten years old, the average age of first diagnosis is 19 years.

Diagnosis is based on the history and presence of the above signs and can be confirmed by testing for hormone levels in blood, specifically the hormone ACTH (Adreno Cortico-Trophic Hormone). Diagnosis can be difficult to confirm in the early stages as tests may yield false negatives.

Treatment is usually by the drug Pergolide, a Dopamine agonist which mimics neural control and inhibits excessive hormone production by the pituitary gland. Reportedly effective in 65%-85% of cases, Pergolide treatment is a management tool not a cure.

Some owners elect not to treat horses with only mild symptoms, managing laminitis via dietary modification, excessive hair growth by clipping etc. Diets should aim for low starch and sugar intake (Low NSC) relying primarily on good quality forage feeds like Lucerne and high fibre sources such as sugar beet and soy hulls with added oil for energy if necessary. Pasture access may need restriction in laminitic horses & ponies as the fructan content in pasture grasses may be enough to precipitate a laminitis attack. Whenever repeated episodes of Laminitis occur in aged horses & ponies, Cushings Disease should be considered. Veterinary advice on management is essential.

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