Sometimes the path to breaking medical ground starts with breaking hearts.
When Fiona, a young Quarter Horse used for competitive reining, developed sacroiliac joint pain, the experts at the NC State College of Veterinary Medicine cared for her with corticosteroid injections into those joints, the accepted protocol.
Fiona belonged to Karie Tucker, a registered veterinary technician in equine medicine at NC State, who often won competitions with the talented mare. After the steroid treatment, Fiona developed a severe case of laminitis, a debilitating hoof condition often caused by metabolic problems, and had to be euthanized.
Part of Fiona’s care team in 2021 was Dr. Kimberly Hallowell, then an equine rotating intern at NC State. She and Schnabel wondered whether there was anything they could have done differently and formed a team with Dr. Katarzyna Dembek, associate professor of equine medicine, and Dr. Caitlyn Redding Horne, an equine sports medicine clinical veterinarian, to investigate.
“We started looking into the literature, and there really wasn’t any solid evidence about what cases are at risk of developing laminitis or even what the safest way to treat those joints is,” says Hallowell, now a Ph.D. candidate in NC State’s Comparative Biomedical Sciences Program with Schnabel as her adviser. “So we decided we should start adding to that literature.”
With two ground-breaking studies linking steroids, insulation dysregulation and laminitis behind them, Schnabel and her team recently were awarded one of the first two $50,000 grants from the Chromatic Fund, named for a show jumper that died following a competition. The fund is a collaborative initiative of the American Association of Equine Practitioners, US Equestrian, Chromatic’s breeder KC Branscomb and The Foundation for the Horse.
The hope is that the NC State research, the basis of Hallowell’s Ph.D. project, will provide equine veterinarians with evidence-based guidance on the safest ways to administer steroid joint injections.
Two Surprising Discoveries
After Fiona’s death, Hallowell had completed her internship and become a resident in internal medicine at NC State. For her residency project, she investigated whether the site of a steroid injection had any effect on a horse’s hormone response to the medication. Fiona’s had been into the sacroiliac joint region deep within the horse rather than into a direct synovial joint environment like a carpus.
The answer turned out to be no, but the horses they studied offered an even more important clue.
“If they already had high insulin to start with, the steroids had a very profound effect on making the insulin much, much higher, which is probably, in retrospect, what happened with Fiona,” Schnabel says. “That led us down this pathway of looking at all the different ways steroids are used and what we should be doing better.”
Hallowell first looked at the recommended dosage of triamcinolone, the most commonly used steroid. Much to Hallowell’s surprise, the recommended total-body dosage of 18 milligrams was based on a paper from the 1970s that was presented at a conference and never even published.
Because the NC State team had found, however, that steroids at any dose appeared to increase insulin in horses — adding to their risk of developing laminitis — they began investigating how those facts fit together.
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 underrecognized, affecting almost a quarter of the sport horses tested despite no reported history of illness or concerns from their owners.
Testing insulin levels before giving steroid treatments to sport horses clearly should be encouraged, Hallowell says.
The Chromatic Study
In addition, because 18 milligrams of triamcinolone has 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, Schnabel and Hallowell started wondering whether it might be safer to treat joints all at once.
That’s the main focus of the Chromatic Fund study.
“We’ve always thought it’s safer to give a low dose repeatedly, but the work that we 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,” Hallowell says. “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, then we inject them again, and it spikes again?”
Steroids also cause the body’s natural cortisol levels to drop, which affects a horse’s health as well. The hormone helps maintain blood pressure, immune function and the body’s anti-inflammatory processes.
“One dose pushes their cortisol to zero basically for a pretty decent amount of time,” Schnabel says. “If we’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? Is that more of an insult to the horse’s system? We don’t know.”
For the study, NC State team members have been testing the blood of the college’s teaching horses to know which might have metabolic disease. Schnabel says they first want to ascertain what effect certain steroid doses have on normal horses.
“We’ll check their responses to either getting a single high dose or a repeated low dose, and that will inform our clinical practice directly,” Schnabel says. “The findings of most of the things we do go to care for our patients and clients in the clinic.”
The study should be complete by spring 2026, she says.
At the American Association of Equine Practitioners annual convention, Schnabel and Hallowell presented the results of their current sport horse study. June 2026, they will share their research at the annual convention of the American College of Veterinary Internal Medicine.
