What is this?
This condition is caused by an enlargement of part of the pituitary gland (pars intermedia) - this enlargement is an age related change and is not cancerous. The pituitary gland is a very important center for hormonal regulation and as the pars intermedia grows, various hormonal changes occur. Together these changes result in variable levels of cortisol in the blood and a loss of the natural rhythmic secretion of cortisol. As a sequel to these changes, horses with Cushings display a complex array of clinical signs
History and presenting signs?
- Usually older horses and especially older ponies
- Weight loss or muscle wasting
- Abnormal bulging of fat pads above the eyes
- Thick, long wavy hair coat with abnormal shedding
- Excessive urinating and drinking
- Lethargy
- Persistent sweating
- Long term recurrent laminitis
- Eye problems
- Recurrent infections
Diagnosis
- History and presenting signs as listed above
- 85% of horses with cushings have the typical long wavy coat mentioned
- Blood sample
- Dexamethasone suppression test
- Response to pergolide therapy
Lab Results and Tests
- A single blood sample is not diagnostic but may give an indication that the horse has cushings
- Blood samples show typical changes in the white blood cell pattern
- The blood work may show signs of secondary infection
- Cortisol levels may be high, low or normal
- Blood glucose may be high
- The most common diagnostic test used is the dexamethasone suppression test
- Two blood samples are needed for this- one before and one several hours after an injection of dexamethasone. The change in cortisol levels between the two samples is used to make the diagnosis of Cushings.
- This test should not be performed in autumn as it may be less accurate at this time of year
Treatment and Management
- Regular dental care
- Good nutritional management
- Careful attention to feet and regular trimming
- A good de-worming program
- Regular clipping and rugging if needed
- Oral pergolide: this is a drug that safely and effectively provides dopamine replacement. Treatment is lifelong and is individually tapered down to the lowest effective dose
- Regular monitoring of blood samples can be a useful tool
