In Part One on this topic, I discussed the symptoms and diagnosis of Equine Cushing’s Disease, or pituitary pars intermedia dysfunction (PPID). In this second part, I’ll discuss treatment and management options.
The two horses in the feature photo from Part One are both being treated for PPID. As you can see from the photo, they look great! Horses can have a future even after this diagnosis, especially if the condition is caught early. However, undiagnosed or untreated horses can experience many problems.
Review of Symptoms
In Part One, I discussed symptoms of PPID that included skin and hair changes, laminitis, abnormal fat deposits, lethargy, and frequent infections due to a suppressed immune system. While some of the symptoms can be managed (like clipping a hair coat that won’t shed out), the impact of an unregulated endocrine disease can be devastating.
Another metabolic problem that often occurs with PPID is called insulin resistance. This means that it takes more and more insulin to push glucose into the cells. The irony of diabetes (lack of insulin production) or insulin resistance (lack of response to the insulin that is circulating) is that the body is starving in the face of plenty of available glucose. This altered metabolism leads to fatty deposits and a significantly increased risk of laminitis. Affected horses lose muscle mass and weight on their toplines and generally appear to be in poor shape.
The current hypothesis is that Insulin Resistance and PPID occur independently, but there is much about this complex series of metabolic diseases that are poorly understood.
Only one approved treatment: Pergolide
The only FDA-approved medication to treat PPID is Pergolide. Pergolide is a dopamine agonist, which means it mimics dopamine. It can bind to the same cell receptors as dopamine. Remember in Part One where I described, “an age-related oxidative stress-induced neurodegeneration of the dopaminergic neurons of the hypothalamus“? This means that the neurons that produce dopamine degenerate, and dopamine levels are low and/or inconsistent. Pergolide “fills in” for dopamine and helps to restore a normal endocrine balance.
Aside from knowing that pergolide is a dopamine agonist, there is much that science doesn’t understand about how it works. However, even though how it works is not fully understood, how it behaves in the body is relatively predictable.
- It begins to work within a few hours.
- It does not accumulate within the body and steady levels can be achieved within a few days.
- It has a half-life of less than 12 hours, which means half of the administered dose is cleared in less than 12 hours.
- Dividing the daily dose into morning and evening doses probably achieves the best results.
High levels of dopamine can suppress appetite. This is one of the most common challenges of initiating treatment in horses. Usually, once dopamine levels stabilize and the horse’s body becomes acclimated to the medication, the horse’s appetite returns.
Prascend is the currently available formulation of pergolide. I believe I used a compounded product way back when my Arabian was diagnosed nearly 20 years ago. Most veterinarians recommend Prascend over compounded formulations, citing stability and consistency as their primary reasons. A starting dose of Prascend will average $2/day, while a compounded formulation is closer to $1/day.
Saying Goodbye to Kari
A few years ago, I blogged about euthanasia from “both sides of the table”. Too many times I have had to send my animals over the Rainbow Bridge. And of course, I have helped many a client do the same thing.
My journey with my Arabian, Kari, was challenging to say the least. We tried reverse shoeing and every possible means of making him comfortable. He was on pergolide. I kept him going for three years.
In late 2005, I was preparing to leave Illinois and return to Kansas. As I mentioned previously, I really never found an equine vet there that I liked. I decided to have my local guy take films and I sent those films back to my vet in Kansas.
I will never, ever forget the phone call from him… “You are risking a catastrophic event if you trailer that horse to Kansas.” Poor Kari’s feet were so damaged that his coffin bone was hovering over his sole. November in the Chicago area consisted of freezing and thawing on a daily basis. The “dry lot” was alternately mud and then frozen hills and valleys. My vet friend was telling me that we were a song and a prayer away from having Kari’s coffin bone push through his sole.
I walked him to the stable next door to meet the vet. His tail was up, he was prancing in the soft, thick grass, and he looked so beautiful. I was such a mess that the vet inquired, “Are you sure you want to do this?” Yes and No. It is a memory seared in my brain.
Life with a PPID horse
A friend of mine is currently dealing with her Cushing’s mare. I asked Linda what led her to seek the diagnosis, and what was life like now? This was her response:
She was lethargic, didn’t seem happy at all. Then she got laminitis. It was spring, still snow on the ground. As far as living with a horse like her, it’s been a real rollercoaster with her seeming to be very unhappy in her life, to then having a few good days. I think often if I would be doing her a favor by putting her down. But then she’ll have a few days where she seems a bit better…
I can so relate to those thoughts.
Next week I will talk about Equine Metabolic Syndrome, followed by information on the nutritional management of horses with metabolic diseases.