Because horses afflicted with equine Cushing's disease often develop laminitis, advances in diagnosis and treatment of Cushing's can help veterinarians better prevent and/or treat the laminitis that stems from it. Nora Grenager, VMD, Dipl. ACVIM, of the Steinbeck Country Equine Clinic, in Salinas, Calif., updated attendees on Cushing's at the Sept. 17-18 Laminitis West Conference, in Monterey, Calif.

Horses with Cushing's (technically known as pituitary pars intermedia dysfunction or PPID) have an eightfold decrease in levels of dopamine (a hormone and neurotransmitter) and its metabolites (breakdown products) compared with nonafflicted horses of the same age. Grenager reported that this is most likely due to localized oxidative stress and noted that evidence is lacking that this decrease is caused by systemic inflammation or systemic oxidative stress. Other, less likely, factors that have not yet been well-evaluated could include toxins or pesticides, genetic predisposition, chronic inflammation or abnormal systemic metabolism, and a diet lacking enough selenium or protein.

Cushing's horses are frequently insulin-resistant, a condition that also can be a factor in non-Cushing's-related laminitis cases. A simple blood test can often identify horses with insulin resistance. Part of the problem with Cushing's is that it can be difficult to diagnose early because horses can present widely divergent clinical signs.

"The ones where we need help are the ones where (the diagnosis) is not so clear," Grenager said. "The bad news is that we don't yet have a great test for those horses. That's what researchers are working on

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