Equine Cushing’s disease (also called pituitary pars intermedia dysfunction or PPID) is not uncommon and has been well described in the Northern hemisphere. However, the presentation and outcomes associated with the disease have not been widely reported in the Southern hemisphere.
An Australian study described the clinical presentation of the disease and investigated factors associated with the development of laminitis, insulin resistance and survival with the geographic location (latitude) of the cases of particular interest.
The clinical records of 274 cases from eight different Australian hospitals were reviewed. Cushing’s had been diagnosed using resting ACTH levels, dexamethasone suppression tests, thyroid tests and necropsy. Laminitis was diagnosed radiographically or at necropsy, and insulin resistance was diagnosed by resting insulin and glucose levels as well as insulin response testing.
Horses with Cushing’s living in warmer, more tropical areas closer to the equator were more likely to present with anhydrosis (the inability to sweat) as well as excessive water intake and urination. About half the horses were lame on presentation, and laminitis affected about 90% of the horses X-rayed. This likely influenced the poor survival rate reported (70%) for animals at 11 months of follow-up. Being a pony, a higher body condition score and treatment with pergolide increased the chances of survival. Insulin resistance affected about 75% of the cases. The authors emphasized that early diagnosis facilitated by good client education, maintaining adequate body condition and treatment with pergolide are important for the effective management and survival of horses and ponies with Cushing’s disease.
— Horn R et al. EVJ 2019;51:440-445