PPID (Pituitary Pars Intermedia Dysfunction aka Cushings disease) or Equine Cushings disease as it is also known is the most common endocrinopathy or hormonal problem that is encountered in horses and ponies. It is thought that 1 in 5 horses or ponies over the age of 15 years, suffers from the condition, although it is increasingly being diagnosed in younger animals.
It is caused by aged related degenerative changes within the pituitary gland of the brain. This results in the secretion of abnormally high amounts of hormones, the most important of which is ACTH (Adrenocorticotrophic Hormone). This excess in ACTH hormone can then cause the adrenal glands to become overactive and secrete high levels of cortisol (a steroid hormone). Cortisol results in an increase in INSULIN levels which are associated with laminitis.
Clinical Signs of PPID
- Laminitis – in 50-80% of cases
- Curly coat (hirsutism) +/- variations in natural spring shedding of the coat
- Sweating and lethargy
- Excessive drinking and urine production
- Weight loss from muscle wasting
- Redistribution of fat e.g. above the eyes
- Increased susceptibility to infection – such as skin infections, parasite infestations and foot abscesses
- Poor wound healing
Confirming the diagnosis
The vet may be suspicious of PPID based on the clinical signs, e.g. laminitis for the first time in an older horse or a long, curly coat. If we suspect PPID we will recommend taking a blood test . 2 tests are commonly used
Requiring only a single blood sample this test is easy to perform and will detect most cases of PPID. If the ACTH is normal but we are suspicious of PPID we will recommend a TRH stimulation test. In cases where PPID is strongly suspected but the result is negative, a further test can be carried out called a TRH stimulation test.
TRH stimulation test
This is the ‘gold standard’ test for PPID. It involves taking a baseline blood for ACTH levels, then injecting the horse with a small amount of the hormone called TRH before taking a second blood for ACTH 10 minutes later. The rise in ACTH between the 2 samples is used to diagnose PPID. This test is very accurate for diagnosing PPID but at the moment cannot be performed in the Autumn.
We may also test the Glucose and Insulin levels in your horse.
There are no cures for PPID. However, there are drugs and management changes that can help your horse to live a comfortable life whilst reducing the risk of laminitis.
Peroglide Mesylate (Prascend)
Prascend is the licensed treatment for PPID in horses. A standard sized horse will begin at a dose of 1 tablet once daily. We recommend taking a further blood sample approximately 4 weeks after starting the medication to check that the hormone levels have reduced and/or are close to normal. If not, the dose may have to be altered.
Your vet may recommend: Clipping of the coat, routine dental and farrier attention, careful worming, special diets and regular checks on your horse’s body weight and general health.
Obese horses release inflammatory mediators from fat which may contribute/speed up the degenerative changes happening in the brain. Keeping your horse fit and in good body condition score will not only improve their overall health but may also help decrease the risk of developing laminitis and PPID.
Autumn time differs…..
There is seasonal variability in ACTH levels in horses, regardless of whether they have PPID or not. From about September to November, ACTH levels naturally rise. However with horses who have PPID this rise tends to be more dramatic. For that reason we suggest re testing horses that may have previously had a negative result earlier in the year and PPID is still a concern. Those horses which are already on Prascend should either be retested to check their ACTH levels are under control or they should have their medication increased during this time by 50%.