What is PPID (Cushing’s) and how do I recognise and support my horse who has it?
Valérie De Clerck
Last updated: 27/10/2025
PPID (Pituitary Pars Intermedia Dysfunction), also called Cushing's in horses, is a disorder of the pituitary gland in the brain where hormone regulation becomes disrupted.
In the brain, there are nerve cells that produce dopamine. In horses with PPID, these cells become damaged. Normally, dopamine inhibits the pituitary gland, a small gland that regulates hormones. When this inhibition disappears, the pituitary produces too many hormones, including adrenocorticotropic hormone or ACTH.
ACTH stimulates the adrenal glands to produce cortisol. In PPID horses, this happens too much and too often. The result is a continuously elevated cortisol level in the body. This affects metabolism, muscle development, fat distribution, coat growth, and insulin function.
Your veterinarian can confirm PPID with a blood test that measures ACTH levels.
Although older horses are at higher risk for PPID, younger horses can also be affected. About 1 in 5 horses over 15 years old and 1 in 4 horses over 20 years old show signs of PPID (Galinelli et al., 2021).
What is the role of nutrition in managing PPID symptoms?
A recent study by Galinelli et al. (2021) highlights the importance of adapted nutrition in horses suffering from Pituitary Pars Intermedia Dysfunction or PPID. Although PPID is usually treated with the drug pergolide, nutrition is now also recognized as a crucial factor in managing clinical symptoms, reducing the risk of laminitis, and maintaining a good quality of life.
When creating a feeding plan, the following factors should be considered, such as:
- Evaluation of body condition and muscle mass. Based on this, the correct amount of energy, carbohydrates, and proteins can be determined.
- Assessment of insulin dysregulation (ID)
- Adjustments according to age and activity level
What are the main symptoms of PPID?
Symptoms of PPID can vary greatly from horse to horse and change as the disease progresses. In the early stages, the signs are often subtle, but over time they become more visible, and more signs may appear.
Pay attention to the following signs, which may indicate PPID:
- Laminitis: often in horses with impaired insulin function (insulin dysregulation)
- Hypertrichosis: a long and curly coat
- Hirsutism: difficulty shedding in spring
- Weight loss and muscle wasting
- Abnormal fat distribution: fat accumulation above the eyes, a potbelly, and sometimes fat on the crest
- Lethargy and depression: due to loss of dopamine-producing nerve celles and elevated cortisol levels
- Polyuria and polydipsia: frequent drinking and urination
- More susceptible to infections
Not every horse shows all the symptoms at once. In the early stage, subtle coat changes or mild lethargy are often noticed. Regular observation is important to detect changes in time.
If you recognize certain symptoms and suspect that your horse suffers from PPID, always make an appointment with your veterinarian.
What is the link between PPID and insulin dysregulation?
Normally, insulin (a hormone) ensures that sugar from the blood enters the cells so they can use it for energy. In insulin dysregulation, the cells no longer respond properly to insulin, so sugar (glucose) remains in the blood too long. The pancreas detects the high blood sugar and thinks “there is not enough insulin,” so it produces even more.
In horses with PPID, the brain produces too much of the hormone ACTH. ACTH causes the adrenal glands to produce cortisol. Normally this process stops once enough cortisol is in the blood, but in PPID this brake no longer works. The increase in cortisol also makes the cells less sensitive to insulin.
This is why one in three horses with PPID often develop insulin dysregulation and are more prone to laminitis.
How is PPID treated?
PPID is a chronic condition that cannot be cured, but the symptoms can be managed with the drug pergolide. This medication is a dopamine receptor agonist that reduces the production of ACTH. This lowers cortisol production and can reduce the severity of symptoms.
In addition to medication, nutrition and regular evaluation play an equally important role in PPID management.
Together with your veterinarian, you can go through these steps to create a complete feeding plan that meets your horse’s specific needs:
- Step 1 Determine the current and desired body condition: PPID is associated with both overweight and underweight.
Overweight: Elevated insulin levels promote fat storage, especially in the crest, tail base, and above the eyes.
Underweight: In later stages of PPID, high cortisol levels can cause muscle loss and depletion of fat reserves.
- Step 2 Determine the presence and severity of insulin dysregulation: The severity is determined by insulin and glucose measurements from the blood. This test is performed by your veterinarian.
- Step 3 Age: Older horses often suffer from dental problems and arthritis. If your horse has dental problems, they should ideally be fed soaked pulp or hay pellets. If your horse has arthritis, provide hay at ground level instead of in hay nets to avoid strain on the neck.
- Step 4 Activity level: Too much energy, especially from sugar or starch, increases the risk of insulin dysregulation and laminitis. Horses that move little burn less energy, causing sugar and fat to accumulate faster. When a horse moves regularly, the muscles use more glucose as an energy source. This lowers sugar and insulin levels in the blood.
Figure 1 shows an overview for assessing and managing horses, ponies, and donkeys with PPID. The chart helps tailor feeding and management decisions to body condition (BCS) and the presence of insulin dysregulation (ID).
Figure 1: Flow diagram with a step-by-step approach for evaluation and feeding management for horses and equids with PPID (Galinelli et al., 2021).
Conclusion
A good feeding plan for horses with PPID requires an individual approach. Body condition, insulin sensitivity, and age must always be evaluated. Combined with medical treatment and regular follow-up with your veterinarian, this helps support your horse’s quality of life with PPID.
Read our next blog on how to adjust your horse’s diet step by step according to weight, age, and insulin sensitivity. You will get practical guidelines and examples for horses with overweight, underweight, and/or insulin dysregulation.
