PPID is one of the most common endocrine (hormonal) disorders affecting horses and ponies. With laminitis being one of the most serious consequences, we thought it timely to bring you a guide to this sometimes confusing condition.

What is PPID?

Pituitary Pars Intermedia Dysfunction (PPID), also known as ‘Cushing’s syndrome’, is a hormonal condition affecting the pituitary gland. However it is now recognised that PPID is different to the canine and human Cushing’s syndrome/ disease. In affected horses and ponies the pars intermedia or ‘middle lobe’ becomes over active (and often enlarged) and produces large amounts of several hormones including adrenocorticotropin hormone or ‘ACTH’. How this rise in hormones leads to clinical signs of PPID is not yet understood.

Is your horse at risk?

PPID is most commonly diagnosed in older ponies although horses and younger animals can also be affected. There does not seem to be a breed or sex bias and in fact, it has been suggested that ponies may be more commonly affected simply because they tend to live longer.

Signs of PPID include

- Failure or later shedding of the winter coat that may become long, matted and curly especially around the legs

- Excessive sweating

- Increased drinking and urination

- Lethargy and poor performance

- A pot-bellied appearance

- Loss of muscle and topline

- Abnormal fat distribution particularly above the eyes, the crest of the neck and above the tail head

- Chronic or relapsing laminitis

- Delayed wound healing, increase in infections of the skin and susceptibility to internal parasites

- Infertility

- Seizures, weakness, blindness and collapse (although these are rare and only seen in very advanced cases)

How is PPID diagnosed?

A test to measure the baseline level of ACTH circulating in the blood is often used to diagnose PPID, with a result above a certain level regarded as ‘positive’. However results are not clear cut as there is a ‘grey area’ between the threshold for ‘normal’ and positive results, particularly in ponies. A more dynamic ‘TRH stimulation test’ which also measures ACTH is therefore sometimes used to confirm the diagnosis.

Diagnosis challenges

Unfortunately the ‘grey zone’ is not the only challenge when it comes to diagnosing PPID.

- ACTH levels are affected by season and are naturally higher in the autumn. Results should therefore be interpreted using seasonally adjusted reference values (provide by the lab).

- Senior horses have naturally higher levels of blood ACTH compared to ‘adult’ horses.

- Stress, exercise and whether or not the horse/ pony has been fasted may affect ACTH levels.

- New research has shown that high starch diets can increase ACTH levels and may lead to false diagnosis. See our previous blog for more details.


Although PPID cannot be cured, with suitable management and veterinary treatment horses and ponies can continue to live happy and active lives for a number of years. Treatment with Prascend, a form of the Pergolide drug licensed for use in horses, can reduce the clinical signs of PPID. A loss of appetite is a common but in most cases temporary side effect. This can often be overcome by stopping treatment until appetite returns and then reintroducing at a lower rate before gradually increasing again to the recommended dose. Always seek advice from your vet before adjusting your horse’s dose.

Feeding tips

- Nutritional management of Cushingoid horses and ponies is very similar to that of a laminitc and therefore providing a diet that is low in starch and sugar should be a priority. This includes sugar and fructan (the storage form of sugar) in grass and hay/ haylage. See our Cushing’s page for more advice.

- Although feeds should be low in sugar, they do not need to be sugar or molasses free.

- Although not scientifically proven, additional antioxidants (vitamin E, vitamin C and selenium) may be helpful. However selenium can be harmful if oversupplied so always seek advice from a nutritionist before introducing any supplements.

- Many supplements claim to improve the clinical signs of PPID but to date, none have been scientifically proven. In fact one study suggested that Vitex Agnus Cactus or ‘Chasetree’ cause further deterioration.

And finally…

A number of other management changes can help to maintain health and improve quality of life in Cushingoid ponies including clipping (especially in summer months), regular eye bathing and increased faecal egg counts. Speak to your vet and/ or contact the Care-Line for more advice.

For more on advice on managing horses and ponies with PPID contact the SPILLERS Care-Line on 01908 22 66 26.