Equine Cushing’s Disease
What is it?
Equine Cushing’s Disease is commonly encountered in older horses and ponies but is now also recognised in equines in their mid – teens.
The condition results from a pituitary gland adenoma (a benign tumour) which secretes abnormally high levels of adrenocorticotropin (ACTH). ACTH stimulates the production of cortisol (a type of steroid) from the adrenal glands. Therefore, high levels of ACTH result in an excessive production of cortisol (Hyperadrenocorticism).
- Thick, long, shaggy coat that is not shed (hyrsutism). Curly in advanced cases
- Excessive drinking and urinating (polyuria/polydipsia).
- Abnormal deposition of fat (crest, bulging of fat pads above eyes).
- Recurrent laminitis, due to high levels of cortisol in the blood Intractable pain secondary to laminitis represents the leading cause of euthanasia in Cushingoid horses.
- Increased susceptibility to infections (especially skin, foot abscesses, thrush) due to the immunosuppressive effect of circulating
- Muscle wastage in advanced cases. Drop-bellied/ ‘Pantomime’ horse
The most practical way of testing for Cushing`s disease in practice is a single blood test to detect ACTH levels.
There is no cure for Cushing`s disease, however there are some drugs available to control the disease.
Prascend (Pergolide) is to date the most effective drug to lower ACTH levels and help alleviating the clinical symptoms. Pergolide is administered once daily and should be given for life after diagnosis of the disease. The dose can be adjusted in relation to individual response. Side effects (anorexia, depression are often transient and resolve after lowering the dose).
Husbandry is also very important in the managing of a Cushingoid Horse, Particular attention should be paid to diet, worming, oral hygiene/dental care, hoof trimming and prompt treatment of infection.
Cushingoid horses with long hair coat should be clipped during the warm season.
Laminitis is probably the most difficult complication to deal with. However, the medical therapy should bring improvement in patient comfort and decreases the likelihood of further bouts of laminitis.