Steroids and Insulin: The Hidden Trigger of Catastrophic Laminitis

Welcome to Conversations in Equine Science. I'm Nancy McClain and I'm joined by Kate Acton.

And this is the podcast where we take equine research and try to make it accessible for horse owners and enthusiasts alike. Remember that with each topic we discuss, it is important to get professional advice before implementing any of the research strategies. Hi, everyone. Welcome to Conversations in Equine Science. I'm Nancy McLean, and I'll be your host for today. I wanted to update everyone on the equine herpes virus. Recently, there's been cases reported in Louisiana, Washington, and Texas.

The cases do seem to be slowing down, but just a reminder, keep up the biosecurity. And if you do travel and compete with your horse, just be very cautious. And when you return to your boarding facility or your farm, you know, make sure you kind of keep that horse separate until you know you're all clear.

This week I also wanted to talk about the American Association of Equine Practitioners Conference. They had an interesting presentation on a current study taking place that's linking steroid use to insulin spikes, and those insulin spikes in sport horses are increasing the risk of a severe form of laminitis. Now, this has always kind of been talked about in hoof care circles that you have to watch using dexamethasone and different corticosteroids.

In this paper, they were actually using triamcinolone, and that steroid is the one that they're actually studying. So, Birgitta Eplin Wheeler did a great article for the American Farriers Journal, and she kind of explained the presentation, where they're at in their research, and when the paper will eventually come out.

Fiona was a young quarter horse used for competitive reining. She developed sacroiliac joint pain, and they decided to inject her with corticosteroid injections directly into those sacroiliac joints, and that is an accepted protocol. However, Fiona developed laminitis, and it was very severe form, and she ended up being euthanized. Now, normally, you would look at an athlete that's competing, that's not overweight, not really a pasture pet, is not being at risk for laminitis.

But the steroid injections create an insulin spike that apparently can induce a laminitic episode. So Fiona belonged to Carrie Tucker, a registered veterinary technician in equine medicine at North Carolina State. She competed and often won with the talented mare, but, you know, unfortunately, due to the deep injections. Fiona did develop the laminitis and, you know, which just practically destroys

the health of the hoof, and she had to be euthanized. So Dr. Kimberly Hollowell at the time was an equine rotating intern at North Carolina State, and she wondered whether there was anything they could have done differently for Fiona. So they formed a team of researchers, one being Dr. Dembeck, another one being Dr. Horn, and they began their investigation into could they reduce the dose? Is it the placement of where the steroid needs to be injected?

Is it different to be injecting the carpus or the knee of the horse into synovial fluid, then directly into the sacroiliac joint? What caused this young, athletic, talented horse to develop laminitis because of the steroid. So they started looking into the literature and there really wasn't much there. Especially regarding what is the safest way to treat those joints. So they just started doing their own research.

They had two groundbreaking studies linking steroids with insulin dysregulation and laminitis. And because of that, they were awarded two $50,000 grants from the Chromatic Fund, which was named because of a horse named Chromatic that died after a competition. And that fund is a collaborative initiative of the American Association of Equine Practitioners, the United States Equestrian Team, Chromatic's breeder, K.C. Branscombe, and the Foundation for the horse.

So they're hoping through this research, they can provide equine veterinarians with evidence-based guidance on the safest ways to administer steroid joint injections. So one of the first things they studied is whether the deep site of the sacroiliac joint had anything to do with the development of the insulin spike.

And the answer was no, but they did find out that if a horse had high insulin to start with, The steroids had a profound effect on making the insulin much, much higher, which is probably what happened with Fiona that led them to look at a better way of giving those steroids or even a better way of administering the treatment.

So they first looked at the recommended dosage, and the surprise was that the 18 milligrams, that's total body dosage recommended, was based on a paper from the 1970s that was presented at a conference but was never published. So they did find that steroids at any dose appeared to increase insulin in horses, and they began investigating how to...

In an ongoing study funded by the Foundation for the Horse, Hallowell looked at the prevalence of undiagnosed insulin dysregulation in sport horses like Fiona and found that dysregulation is far under-recognized, affecting almost a quarter of the sport horses tested. Despite no reported history of illness are concerns from their owners. Now, testing insulin levels before giving steroid treatments to sport horses should be encouraged.

And so often we tend to look at a horse's propensity for developing laminitis is they're overweight. They clearly have equine metabolic syndrome with their adiposity. Their high body condition, you know, there's certain a crusty neck and then those fat deposits. So these horses don't have that and yet they still have high insulin levels.

So because 18 milligrams of triamcinolone had been the standard total body dose, horses with more than one affected joint often wait a few months between treatments. Knowing how negatively steroids can affect insulin levels, Hallowell started wondering whether it might be safer to treat joints all at once.

That really is the main study now, and that's what the Chromatic Fund is interested in them finding out. So they always thought it was safer to give a low dose repeatedly, but the work that they have done and other groups have done looking at triamcinolone has found that in some of these horses, insulin rise can last upward of two weeks after a dose. Are we actually doing more harm than good by letting these horses have an insulin spike for two weeks?

Get back to normal for a week or two and then inject them again. So steroids, you know, can cause the body's natural cortisol levels to drop, which affects a horse's health as well. And the hormone helps maintain blood pressure, immune function, and the body's anti-inflammatory processes. So their feelings are now that one dose pushes their cortisol to zero basically for a pretty decent amount of time.

If they're already maximally suppressing cortisol with a low dose of steroids, should we just give the high dose rather than maximally suppress it? Let it go up, then knock it down again. She thinks that's more of an insult to the horse's system, but in any case, that's what they want to know. What is the proper protocol for giving these steroids?

So for the study, North Carolina state team members have been testing the blood of the college's teaching horses to know which might have metabolic diseases. They first want to uncover what effect certain steroid doses have on normal horses. So they'll check their responses to either getting a single high dose or a repeated low dose, and that will tell them. Kind of what clinically this study might be leading to as far as giving veterinarians proper directions.

The findings of most of the things we do go to care for our patients and clients within the clinic.

The good news is this study should be completed by spring 2026. When that paper comes out, Kate and I will definitely get together and talk about it because I think the thing about this is uncovering that even athletic horses can have these insulin spikes going on. And from, you know, just visibly looking at them, you would never know that. So, you know, maybe if a horse has has suffered an injury, maybe before anything is done, we take a blood test and check their insulin levels.

So that's about it on this week for this paper. I just wanted to share this. If it saves one horse from going through laminitis, it was worth my time and effort. So you can get a hold of me at nancy underscore mcclain seven on instagram we have a facebook page as well conversations in equine science give a shout out let us know if there's any further research you want us to cover and as soon as this paper comes out we'll do an episode on it thanks.

Thanks so much for listening and we'll be back next week. Thank you for listening. And if you've enjoyed this podcast, give us a five-star review from wherever you listen from. Also, drop us a line or follow us at Nancy underscore McLean seven on Instagram. Thanks so much, everyone. Have a great week. Bye-bye.