Learn how veterinarians diagnosed and managed six real-life equine Cushing’s cases.
We all know what a horse with equine Cushing’s looks like, right? He’s an old retired guy with a long, curly coat and sore feet. He’s kind of fat in some places, skinny in others.
This type of “textbook” case, however, is far from standard. Also known as pituitary pars intermedia dysfunction (PPID) or hyperadrenocorticism, equine Cushing’s disease leads to an overproduction of hormones such as adrenocorticotropic hormone (ACTH) and cortisol. Classic signs include, yes, an abnormal hair coat and a failure to shed, but also abnormal sweating, loss of muscle mass, and increased water intake and urination, among others.
If and when Cushing’s horses get to the point of looking like the stereotypical case, it’s often in a very late stage of the disease, veterinarians say. And as with many illnesses, the longer we wait, the harder it is to fix.
The good news is the opposite is also true, says Sabine Ware, BVSc, CERP, equine veterinarian at The Vet Practice, in Victoria, Australia. When diagnosed early and treated promptly and properly, PPID horses have the best chance of leading normal lives.
Melissa Restifo, DVM, Dipl. ACVIM, internal medicine specialist at Brandon Equine Medical Center, in Florida, agrees. “Diligent owners are paramount for that,” she says. “They pick up on subtle signs, meaning we can treat the disease before it becomes a real problem.”
In this article Ware and Restifo share real-life stories of Cushing’s horses they’ve treated that stray from the classic scenarios.
Andy: The lethargic one with changes in body shape
12-year-old Australian riding pony cross gelding
Andy was a “very loved pet” who had been used for leisure riding and harness driving. A plump sorrel pony gelding with a body condition score (BCS) of 5 out of 9, he stood about 14 hands.
“He was the calm soul of the farm, with a kind eye and relaxed personality among a farm full of high-spirited dressage horses,” Ware says.
Andy’s owner first noted that her pony was developing strange white spots, about 2 inches in diameter, across his body. “His coat was quite short and shiny, and overall he looked like a healthy pony,” Ware says. “He didn’t have that long curly coat that most people consider to be classic.”
Over the next few months he became increasingly lethargic and finally “ended up with a big, pendulous abdomen,” she says. About the same time he came down with subtle signs of laminitis, a common side effect of PPID if affected horses’ insulin levels are high. “He didn’t get excruciating pain—just increased pulses (in the feet) and very slight (hoof) changes,” she says. “In general, all his signs were mild and vague.”
Indeed, this confusing case didn’t shout “Cushing’s” in the beginning, says Ware. At first she suspected a viral or an immunosuppressive disease and tested accordingly. She also tested his thyroid function and for insulin resistance (IR, a decrease in tissue sensitivity to insulin that often accompanies PPID). And, just to be sure, she ran an ACTH test for equine Cushing’s. The tests showed Andy had both PPID and IR.
Ware started Andy on a daily low dose of the FDA-approved PPID drug, pergolide, which comes in tablet form and is designed to lower ACTH production. She and Andy’s owner also put him on a restricted diet to control his IR.
Within a year the pony transformed completely despite a few initial laminitic flareups. “All his spots went away, his abdomen tucked back up, his laminitis got under control, and he went back to being his brighter self,” Ware says.
Andy benefited from his medication over the next four years, feeling great. He was euthanized due to an unrelated injury at age 16.