Challenges of Cushing's Disease Diagnosis and Treatment

We know Cushing's disease (or pituitary pars intermedia dysfunction—PPID—as it's more scientifically called), simply put, is an "old-horse disease" that results in metabolism disturbances and an abnormally heavy hair coat. But when it comes to testing and treatment, there are about as many opinions as there are people to ask.

Luckily, Harold Schott, DVM, PhD, Dipl. ACVIM, professor of large animal clinical sciences at Michigan State University (MSU), discussed the challenges of PPID diagnosis and treatmen at the 2006 AAEP Convention.

"Owners have really pushed us to learn more about this disease," he began. "Unfortunately, I might not leave you with a totally clear picture, because a lot of what we know is still based on experience rather than scientific data."

Pituitary pars intermedia dysfunction describes altered activity of the pars intermedia lobe of the pituitary gland. Schott first described the prevalence of PPID clinical signs seen in various studies: hirsutism (excessive haircoat) 47-100% of affected horses; muscle wasting, 35-88%; chronic laminitis, 24-82%; polyuria/polydipsia (excessive urination and chronic, excessive thirst/intake of fluid), 17-76%; hyperhidrosis (excessive sweating), 14-67%; abnormal fat deposition, 9-67%; chronic infections, 27-48%; lethargy, 43-82%; neurological signs, including seizures, 6-50%.

"My subjective impression is that age at onset of clinical signs is important; the younger ones (at onset) do worse," said Schott.

"Laminitis is the clinical problem we deal with the most," he commented. "It's our main reason for looking at these horses. Here's a take-home message: Evaluation for PPID is warranted in horses more than 15 years old that develop insidious (gradual) onset laminitis."

Get research and health news from the American Association of Equine Practitioners 2006 Convention in The Horse's AAEP 2006 Wrap-Up sponsored by OCD Equine. Files are available as free PDF downloads.

About the Author

Christy M. West

Christy West has a BS in Equine Science from the University of Kentucky, and an MS in Agricultural Journalism from the University of Wisconsin-Madison.

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