Cushing's syndrome in horses, also known as Equine Cushing's Syndrome (ECS) or Equine Pituitary Pars Intermedia Dysfunction (PPID), is a common hormonal disorder in older horses. It is caused by a malfunction of the pituitary gland, a gland in the brain, which leads to an overproduction of the hormone ACTH. The increased ACTH level then leads to an increased release of the stress hormone cortisol, which has an effect on various bodily functions. The consequences of Cushing's syndrome are correspondingly diverse. It is estimated that up to 20% of horses over the age of 15 can be affected.
Symptoms
Equine Cushing's syndrome (ECS or PPID) in horses shows a variety of symptoms that are due to hormonal imbalances in the body. Here are the main symptoms:
- Long, curly coat (no complete loss of winter coat)
- Increased sweating
- Laminitis
- Weight loss and muscle loss
- Fat pads, especially over the eyes, on the neck and at the base of the tail
- Increased water intake and urine excretion
- Fatigue and tiredness
- Recurrent infections
- Changed body shape (some horses develop a pendulous belly and lose their typical body shape)
- Behavioural changes: Horses with PPID may show behavioural changes, such as increased irritability or apathy.
Causes
Cushing's syndrome has the following triggers in particular:
Ageing process
Similar to humans, certain organs and bodily functions in horses can no longer function as well with age. In older horses, the pituitary gland is often affected.
Malfunction of the pituitary gland
The pituitary gland is an important gland in the brain that produces many hormones. In horses with Cushing's syndrome, this gland does not work properly and produces too much of certain hormones, especially ACTH.
Overproduction of cortisol
The overproduction of ACTH stimulates the adrenal cortex to produce more cortisol. Cortisol is a stress hormone that can be harmful in excessive amounts and causes many of the symptoms of Cushing's syndrome.
Genetic predisposition
Some horses may have a genetic predisposition to developing Cushing's disease, although the exact genetic factors are not yet fully understood.
Long-term stress and metabolic problems
Chronic stress and metabolic problems can increase the risk of developing Cushing's disease. Horses that are under stress for a long time or suffer from other hormonal or metabolic disorders may be more susceptible.
Diagnosis
The diagnosis begins with a thorough clinical examination by one of our vets, who will look for the typical symptoms. In addition, information about the horse's age, behavioural changes and previous health problems will be requested.
Specific laboratory tests are carried out to confirm the diagnosis. The ACTH test measures the level of the hormone ACTH in the blood, which is often elevated in horses with Cushing's syndrome. A blood sample is taken and analysed in the laboratory.
The dexamethasone suppression test (DST) is another test, in which the horse is administered dexamethasone, a corticosteroid. This would normally suppress the production of ACTH and therefore also cortisol. Blood tests before and after administration show whether the cortisol level drops accordingly. In horses with Cushing's syndrome, however, the cortisol level often remains high.
In rare cases, imaging techniques such as ultrasound or MRI can also be used to examine the pituitary gland directly.
As Cushing's syndrome is a chronic disease, long-term observation of the symptoms over a longer period of time is helpful. Regular veterinary check-ups are important. In addition, other diseases that can cause similar symptoms must be ruled out. These include diabetes insipidus, thyroid disease and other hormonal disorders.
Treatement
Cushing's syndrome cannot be cured, which is why treatment is aimed at controlling the symptoms and improving quality of life. Various approaches are used in combination. The main treatment consists of administering medication that regulates excessive hormone production.
In addition to drug treatment, the right diet plays an important role. A diet low in sugar and starch is crucial as horses with Cushing's syndrome are more susceptible to laminitis. The diet should be high in fibre, such as good quality hay, and may include special feed supplements for horses with metabolic problems. Supplements with antioxidants, vitamins and minerals can also be helpful to boost the immune system and improve overall health.
Good care and "proper management" are also crucial for treatment. As horses with Cushing's disease often have a thick, curly coat, regular brushing and clipping is necessary to reduce the risk of skin infections and overheating. Regular hoof care by a competent farrier is important to prevent or treat laminitis. In addition, stress can exacerbate the symptoms of Cushing's disease, so a calm, stress-free environment and a regular routine for the horse is of great importance.
The quality of life of horses with Cushing's disease can be significantly improved through a combination of medication, appropriate nutrition and careful management. Regular veterinary check-ups are necessary to monitor the horse's condition and adjust treatment accordingly.