Understanding PPID (Equine Cushing's Disease)

Written By: Lauren Alderman DVM, CVA, CVSMT

Written By: Lauren Alderman DVM, CVA, CVSMT

What is PPID?

PPID, or Pituitary Pars Intermedia Dysfunction, is sometimes referred to as equine Cushing’s disease. The cause of this condition in equine patients is different from the cause of Cushing’s in human and canine patients, so equine veterinarians typically refer to the condition as PPID.

In horses, PPID results from an enlargement of a specific part of the pituitary gland. This gland is located at the base of the brain, and its enlargement leads to over-production of certain hormones.

Could my horse have PPID?

PPID is one of the most common conditions affecting horses over 15 years of age. Common signs that might lead your veterinarian to suspect PPID include:

PPID Horse with hair coat changes, unable to shed out.

PPID Horse with hair coat changes, unable to shed out.

Horse with abnormal fat deposits across neck, shoulders, and rump.

Horse with abnormal fat deposits across neck, shoulders, and rump.

  • Recurrent laminitis

  • Recurrent hoof abscesses

  • Changes in attitude

  • Changes in hair coat

  • Loss of topline

  • Recurrent infections

  • Abnormal sweating

  • Abnormal fat deposits

  • Infertility

  • Tendon/ligament issues

  • Dental issues

  • Excessive drinking/urination

How is PPID Diagnosed?

We typically recommend one of two common tests for PPID.

Resting ACTH (adrenocorticotropic hormone)

This test requires a blood draw using a specific tube. An elevated resting ACTH level indicates a positive diagnosis of PPID. Unfortunately, a ”normal” result does not definitively rule out PPID.

TRH Stimulation Test (thyrotropin Releasing Hormone)

This test also measures the level of ACTH, but involves comparing the horse’s baseline level to that of a sample taken exactly 10 minutes after administration of an intravenous medication. A horse with PPID will have a more substantial elevation of ACTH in the second sample than what would be detected in a horse without PPID. A TRH stimulation test may be recommended if your horse has early clinical signs of PPID, or if their resting ACTH level is normal despite clinical signs of PPID.

How is ppid managed?

Our goal in treating horses with PPID is to improve their overall quality of life.


PPID can be managed with a medication called pergolide. Prascend tablets are currently the only FDA-approved formulation of pergolide available in the US. The most common side effect seen with this medication is a temporary decrease in appetite, although your veterinarian can recommend ways to avoid this side effect.

Horses being treated with pergolide should be monitored for efficacy over time, as the dose may need to be adjusted. Monitoring by repeating the blood test used to diagnose the horse can be performed after 30 days, while evaluation of clinical signs can be done after 60 days.

Some horses with PPID that do not respond well to pergolide therapy can be given another medication called cyproheptidine. Your veterinarian can recommend the best medical therapy for your individual horse.

Diet and wellness

Special attention should be given to providing routine wellness care for horses diagnosed with PPID. Talk with your veterinarian about their recommendations for a dental and parasite control program. Horses with PPID should receive regular farrier work, and their diet should be based largely on their body condition.

Clinical signs of PPID should be managed as well. For example, your veterinarian may recommend body clipping a horse with PPID to help keep them comfortable during the hot summer months.

Some horses with PPID may also have insulin dysregulation (sometimes referred to as insulin resistance or equine metabolic syndrome). Talk with your veterinarian regarding diagnosis and management of these conditions.