What is PPID?

Pituitary Pars Intermedia Dysfunction or Cushing’s Syndrome as it’s more commonly known, is a disorder affecting the endocrine system, typically seen in older horses but it has been diagnosed in horses and ponies as young as 7.

The disorder develops when nerve cells (neurons) deteriorate in a region of the horse’s brain called the hypothalamus. It is these neurons that are responsible for regulating the pars intermedia, a part of the pituitary gland that controls the body’s hormones. Without nerve input, the pars intermedia begins to grow and produce excess levels of hormones that result in the clinical signs of PPID:

  • A long, curly coat (hypertrichosis)
  • Delayed seasonal coat shedding
  • Regional adiposity (fat pockets)
  • Laminitis, often recurring
  • Recurrent infections such as sole abscess
  • Excessive or abnormal sweating
  • Loss of muscle and ‘pot-belly’ appearance
  • Excessive drinking and urination (polydipsia and polyuria)
  • Bulging above the eyes


Diagnosis of PPID is relatively straight-forward and the clinical signs may be enough for the vet to diagnose alone, but often a blood test is still important to indicate hormone levels. There are one of two tests your vet may do. For horses with obvious signs of the disorder, a blood test is taken to determine the levels of the hormone ACTH (adrenocorticotropic hormone), which is raised in horses with the disorder. A horse with PPID will show hormone levels above the seasonally appropriate range.

For horses or ponies showing early or mild signs of the disorder, a TRH Response test is likely to be used as the method of diagnosis. The vet will intravenously administer the hormone TRH (Thyrotropin-releasing hormone) and obtain two blood samples, one prior to the TRH administration and one following, to determine whether the levels of ACTH increase excessively, to signify the horse is positive for PPID.­­


Lots of horses and ponies diagnosed with PPID can go on to live long and healthy lives. Careful management may be sufficient in mild cases, however the vet will prescribe medication for affected horses.

Pergolide is the medicinal drug typically prescribed for horses with the condition. This works by suppressing the tissue enlargement within the pituitary gland, resulting in a decrease of ACTH production and thus a reduction in the clinical signs.

Besides medication, there are several ways you can manage your PPID positive horse or pony, to keep him more comfortable.

  • Regular check ups from the vet, dentist and farrier as the immune system is weakened and therefore infections are more common
  • Clipping regularly if hypertrichosis is a clinical sign
  • Decrease the nonstructural carbohydrates in the diet to reduce laminitis risk
  • If the horse can be exercised, keep him relatively fit to slow the rate of muscle wastage

If you suspect your horse or pony is showing signs of PPID, please contact your vet.