Disease Du Jour: PPID in Horses

Cushing's disease in horses, also known as PPID, can have subtle clinical signs or cause deadly laminitis.
hairy horse PPID Cushing's
Cushing’s disease is also known as pituitary pars intermedia dysfunction or PPID. Clinical signs include a hair coat that doesn’t shed normally, abnormal thirst (polydipsia) and excessive urination (polyuria).

In episode 88 of the Disease Du Jour podcast we talk about PPID in Horses with Harold Schott, DVM, PhD, DACVIM.

Schott is a Professor of Large Animal Clinical Sciences at Michigan State University College of Veterinary Medicine. He’s a native of Ohio who was an avid polo player through high school and college.

The very first month Dr. Schott was in practice, his boss went on vacation, and he was left to manage a horse with chronic renal failure. It was that early case that stimulated a career-long interest in the urinary tract and electrolyte balance in exercising horses. He studied the effect of exercise on kidney function during his PhD. Dr. Schott became involved in endurance racing as an official veterinarian, and he has completed a 25-mile endurance ride. Dr. Schott often travels to collect information from endurances races in Michigan, as well as nationally and internationally. Over the past couple of decades he’s developed an interest in endrochrine issues from the demand of clients with older horses that have PPID.

As we know, Cushing’s disease is also known as pituitary pars intermedia dysfunction or PPID. Two primary clinical signs are abnormal thirst (polydipsia) and excessive urination (polyuria).

Schott said PPID is still under-recognized by horse owners and veterinarians. “One of the ways I think of PPID is to think of Parkinsons…it’s a brain disease,” said Schott.

He said he often questions horse owners about whether the horse shed out normally or if it took longer. He said vets and owners should look for areas of longer guard hairs on the hind and forelimbs, under the jaw and along the jugular groove. He said horses with PPID will have a loss of topline and will be more lethargic—”not have the same energy level,” explained Schott.

He added that the most devastating clinical sign of PPID is laminitis. Schott said the question there is whether the laminitis is caused by PPID or insulin dysregulation. He said there can be overlap.

Schott noted the resources below from the Equine Endocrinology Group at Tufts.

Topics covered in this podcast include:

  • How common is PPID in general practice?
  • Clinical signs
  • Diagnosis
  • What is the pathophysiology of Cushing’s disease?
  • Humans and dogs also have Cushing’s disease, how is it different in horses?
  • Laboratory findings of Cushing’s horses?
  • Treatment and management


Equine Endocrinology Group

Recommendations for the Diagnosis and Treatment of Pituitary Pars Intermedia Dysfunction (PPID) Page 2 Revised October 2021 by the PPID Working Group

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