cushings

Equine Cushing’s disease most commonly occurs in horses aged 19years or older but can occur in horses of a much younger age.

Clinical signs of the disease include:

• Polyuria (increased urination)
• Polydipsia (increased drinking• Polyphagia (increased appetite)
• Weight loss
• Muscle wastage
• Hirutism (thick, curly coat with delayed shedding)
• Laminitis
• Supraorbital (above the eyes) fat pads
• Lethargy and depression
• Hyperhidrosis (increased sweating)

There is no significant breed or gender predilection, but studies have shown that ponies are more commonly affected than horses.

Diagnosis

Diagnosis is usually made by the presence of one or more of the above clinical signs, signalment (age, type etc) and diagnostic tests. The tests that are most commonly used are:
• Basal ACTH level testing – this is best carried out during the months of August – October as there is a seasonal rise in the levels of ACTH at this time which gives us an increased diagnostic rate. It involves a simple blood test.

• The overnight dexamethasone suppression test (ODST) – this is not very popular anymore due to the more involved nature of the test and also because of the risks associated with dexamethasone administration in horses with a suspected elevated level of steroid already in their system.
• Thyrotropin-releasing hormone (TRH) stimulation test – this involves injecting TRH into the horse and then collecting a blood sample 2-10 minutes after administration. However, TRH is not licensed in horses and some adverse reactions have been seen. These are usually short lived and not severe.

Treatment

Treatment is aimed at reducing the clinical signs of Cushings rather than curing the disease. It is also about improving the quality of life of your horse, with this in mind treatment consists of:
• Clipping excess hair to reduce sweating
• Treating secondary infections
• Increasing weight with diet management
• Treating any laminitis that may occur.

Medical management consists of using a dopamine agonist (pergolide) which comes in the commercially available form of Prascend. This is started at an initial dose of 2g/kg/day. Bloods tests measuring ACTH levels should then be assessed with a repeat blood sample 30days after the initial blood test confirming Cushings. This way doses can be adjusted as required. After this 6monthly repeat blood tests are recommended, these are best carried out in autumn and spring as this is when naturally occurring peaks in ACTH will occur

Prognosis
Generally the prognosis with Cushings is good; however, this is a lifelong condition that requires lifelong treatment and management.