Cushings disease is primarily a hormonal disorder caused by malfunction of the pituitary gland, located at the base of the brain.
The pituitary is often referred to as the ‘master gland’ as it produces various hormones and substances which control body functions via other glands including the adrenal glands.
Overactivity (over-working) of the pituitary causes enlargement of the part of the gland called the ‘pars intermedia’ which then presses on the ‘Hypothalamus’ gland interfering with control of body temperature, and production of endorphins and dopamine. Abnormal sweat patterns and depression are characteristic of Cushing’s horses and ponies.
Over-activity of the pituitary gland leads to over-production of:
- ACTH (adrenocorticotrophin hormone) which causes the adrenal glands to over-produce stress hormones like cortisol, increasing blood sugar and insulin levels and suppressing the immune system. ACTH levels are one of the markers used to diagnose Cushings
- MSH (melanocyte stimulating hormone) leading to abnormal hair growth and shedding patterns
Clinical signs of ‘Cushings’:
- More common in ponies
- The average age of onset is usually over 15 years but can occur in animals as young as 7.
- Abnormally long hair-coat and failure to shed their coat in spring.
- Poor coat colour
- Abnormal sweat patterns and inability to regulate body temperature
- Muscle loss and wasting especially along topline, sway-back
- Loss of lower abdominal muscle tone leads to pot-bellied appearance
- Fat deposits above the eye
- Excessive urination and drinking
- Chronic or recurring laminitis
- Lethargy or dullness
- Poor wound healing
- Failure of the ‘peripheral’ immune system causing skin conditions, hoof abcesses, conjunctivitis, gum disease, pneumonia
Lack of intervention and treatment will allow the disease to progress, causing:
- Persistent lactation
- Mild anemia
What to do:
This depends on the progression of the disease and the state of their dentition. For horses exhibiting the milder signs then the diet change recommended in ProvideIt plan can lead to significant improvements.
Ponies that have not shed for years have shed their coats normally and when their winter coat grows it has not got the curly look.
It is no coincidence that horses and ponies who have a history of being metabolic and laminitic are prime candidates for Cushings Disease as they get older. Year after year of grazing the wrong grasses in the ‘wrong’ stage of growth eventually takes its toll.
Metabolic or obese horses and ponies are often kept on ‘Jenny Craig’ paddocks for long periods in an attempt to prevent them putting on weight. Unfortunately grass kept short like that are prone to potassium/nitrogen spikes and does not contain sufficient nutrition to keep the horse healthy. The micro-organisms of the hind-gut flora are starved of the coarse, fibrous material they need to ferment which in turn ‘feeds’ the horse.
Providing the teeth are still good the deletion of the short, stressed grass with the addition of hay and salt to these horses diet makes a huge difference.
Except in more advanced cases where the horses quality of life is clearly compromised, I recommend making diet changes initially. This will reduce the possibility of a laminitic episode.
Consult your veterinarian to confirm diagnosis and your equine dentist to assess their dentition.
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