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Equine Cushing’s Disease StudiedBy Kentucky Equine Research Staff · October 7, 2013

Equine Cushing’s disease, also known as pituitary pars intermedia dysfunction (PPID), is caused by a tumor or enlargement in the pars intermedia of the pituitary gland. This condition leads to oversecretion of cortisol by the adrenal gland. Affected horses may show signs such as increased thirst and urination, loss of muscle mass, an increased susceptibility to infection, and a long hair coat that doesn’t shed normally.

A research group from the University of Liverpool’s Equine Internal Medicine department conducted a survey of 325 aged horses in Australia whose owners agreed to have the horses examined by a study veterinarian. The owners sent information by mail for analysis by the researchers.

The examining veterinarian collected blood samples and diagnosed PPID in some horses on the basis of adrenocorticotropic hormone concentrations that exceeded levels above reference ranges corrected for seasonal variation. Out of the group, 21% of horses were diagnosed with PPID. Those horses were significantly older (average 24 years) than non-PPID horses. No associations were found between disease diagnosis and gender, breed, or body mass index, although aged horses diagnosed with PPID were more likely than aged nondiagnosed horses to have a history of laminitis. The study group concluded that Cushing’s disease is significantly associated with aging.

Researchers recommended that owners of older horses should have their equines tested to find out whether the horses are already affected and to establish baseline values to monitor disease onset or progression.