Pituitary Pars Intermedia Dysfunction

It's a lot easier to just call it PPID, or as many people call it, Cushing's Disease. After that post I did a week or so ago, I realized that I hadn't really done my due diligence. I heard "Cushing's Disease" a year ago January and simply gave Speedy his pill assuming that was that.

That wasn't really that, and unfortunately, that doesn't have a simple diagnosis, treatment plan, or recovery phase. The reason there is so much contention over the appropriate treatment of PPID is because there's a lot the medical establishment doesn't know. And even more so for horses in the earliest stages of the disease; horses like Speedy.

I spent a lot of time last week researching the disease; the Laminitis Site and the ECIR Group were good resources. PPID is a rabbit hole that goes on for miles and miles. There is no bottom, no end, no definitive answer. After realizing that I didn't really need to know the exact hormonal processes that were happening, I scanned the more technical aspects of the disease and focused my energies on treatment.

Several things jumped out at me. First, it is not necessarily easy to interpret the ACTH levels. To simplify things, the ACTH level indicates whether things are under control or not. A "normal" range is somewhere between 9 - 35. One problem with checking the ACTH level is that it can rise from a variety of factors, none of which mean that a horse even has PPID. Stress, whether from trailering, pain, or even seeing the vet, is enough to rocket up the ACTH level.

The time of year the test is given can also raise the levels. There is a well documented seasonal rise in all horses. From late summer, around August, all the way through to the end of December, all horses will experience a rise in their ACTH levels. Scientists don't exactly know why, but the reasoning is that it helps horses prepare for winter.

Some PPID experts encourage testing in the fall to see how high the ACTH levels rise. Others recommend testing when the ACTH levels should be at their lowest, January and February, in order to get a baseline measurement. There's no limit to the amount of times that you can test, it's simply a blood draw, but it's not cheap. I didn't look too closely at my last bill, but I think the test runs around $150.

The second thing I spent a lot of time researching was the dosage. The manufacturer recommends dosing by weight. In addition, the recommended maximum dose is 2 pills per day. While there are horses being treated with 5 - 10 or even more pills per day to control their symptoms, there is currently no published research using doses higher than 5 mg for a 1,000 pound horse.

Regarding the appropriate dosage, it should be noted that there is no cure for PPID. Prascend won't cure a horse; all it can do is control the symptoms. Even then there is no guarantee that Prascend will control them. That's why PPID horses still suffer laminitic events and ultimately death.

From the Laminitis Site, "PPID is a progressive disease, and the amount of Pergolide required to control the symptoms is likely to increase as the horse ages. Some horses only need Pergolide during the seasonal rise in the early stages of the disease. Many horses need an increased dose of Pergolide during the seasonal rise."

Once I felt that I better understood the disease, I gave Dr. Tolley a call. And as I knew he would, Dr. Tolley spent quite a bit of time with me formulating a plan for Speedy. The first thing that we both agreed upon was that Speedy is nearly asymptomatic. Of all the early signs of the disease, the only one that Speedy has is frequent infections, and those are limited to his feet in the form of abscesses. And interestingly, those have all occurred during the seasonal rise of the ACTH levels (late summer through early winter). 

Dr. Tolley had three possible explanation for why Speedy's ACTH levels could have risen so dramatically while being treated with Prascend and showing no other clinical signs. A horse with levels like Speedy's should have shown something else to indicate the disease. First, Dr. Tolley posited that Speedy might not be getting the dose. 

We talked about how the ranch owner doses Speedy. She stands with him until she hears him crunch it. Even then she watches closely for the "spit out." It happens every once in a while, but she's quick to locate it and pop it back in his mouth. She gives it to him in a place where it can be easily found if he does spit it out. 

Speedy isn't the first PPID horse she's managed. Her own mare, Lilly, had PPID for more than 6 years before succumbing to laminitis. The ranch owner is an old hand at effectively delivering the pill. Dr. Tolley agreed that Speedy is more than likely getting his dose.

​The second reason that Speedy's ACTH levels might have risen could be due to a "false positive". It is very possible that when Speedy's blood was drawn, he was under a high degree of stress, which we know raises ACTH levels. He had traveled nearly 40 minutes in the trailer, he was worried about Izzy's whereabouts, he was still dealing with a draining abscess, and he was facing the man who always sticks him with needles.

The third reason Speedy's ACTH levels might have risen is that his PPID symptoms are unaffected by the 1 mg. dose. This is a worst case scenario as it would suggest that his symptoms might not be controlled by Prascend. For now, we're going to assume his ACTH levels were high due to stress.

The next thing I wanted to know was how confident Dr. Tolley is that Speedy truly has PPID. When asked point blank how confident of his diagnosis was he, Dr. Tolley responded that yes, even though Speedy's symptoms are nearly non-existent, the fact that he has elevated ACTH levels combined with fall and winter abscesses, his diagnosis stands. Was there something else it could be, was there another explanation, should we look at something else? To each question, Dr. Tolley answered no.

Dr. Tolley has never resented my questions. He's never been offended when I've asked for a second opinion or when I've consulted a different medical professional. And in this instance, his response was the same; do more research, ask more questions, consult other doctors. He welcomed my perseverance and thanked me for really thinking about how to approach this disease.

So where does that leave us? First, we decided to reduce the dosage from 2 pills to 1 and a half pills for now. Dr. Tolley wants Speedy to maintain that dose for 90 days. At the beginning of June, he will come out to the ranch and do a blood draw with the intent of lowing Speedy's stress level. Getting the sample back to the hospital quickly will be a slight issue, but he thinks he can do it without affecting the results.

Based on that blood draw, we will either maintain the current dose or return to the 1 mg dose. We also have it in mind that we may need to raise the dose in anticipation of the seasonal rise in Speedy's ACTH levels. To determine that, we may need to do another blood draw in August.

When Speedy was very first diagnosed with PPID, I asked how many pills we could give him. Dr. Tolley's response was the same then as it is now. We can give him as many as we want, but in his experience, three or more pills haven't controlled the symptoms any better than the maximum recommended dosage of two pills. Every horse responds differently. We'll just have to wait and see.

When I pressed him for next steps, I was again met with his reluctance to answer. It was only when I finally explained that I wasn't searching for a miracle that he quit evading my question. Over the phone I could hear him give a sigh of relief. Essentially, we're already doing everything we can. That was his answer. We'll do bloodwork. We'll adjust his Prascend up and down. And we'll pray. I can do that.

Many of you have recently expressed your feelings about me as a human being. While I welcome comments and never delete the ones that are harsh or critical, I would ask that if you do choose to comment on this post that you do so in a way that fosters respectful conversation. I may not be making the same choices that you would make, but I am making them in consultation with my veterinarian. His opinion matters a lot more to me than does yours.

And life goes on.