Horse Racing

Study linking Thyro-L supplementation with cardiac arrhythmias


A study done on six Standardbred racehorses associated supplemental thyroxine use with cardiac arrhythmias and concluded that the supplement could also be a contributing factor to fracture.

The results of this study appear in the May 2022 issue of the Equine Veterinary Journal. Janice Kritchevsky, Carla Olave, Stacy Tinkler, Melissa Tropf, Kathleen Ivester and Laurent Couetil from the Department of Clinical Veterinary Sciences at Purdue University and Lauren Forsythe at the Davis School of Veterinary Medicine at the University of California-Davis conducted the study with funding from the Guelph Equine Center in Ontario. They initially published the results in September 2020, and the study was first published in 2021.

A series of sudden deaths in racehorses linked to trainer Bob Baffert’s stables at the former Betfair Hollywood Park in late 2011 and early 2013 brought attention to the use of levothyroxine (Thyro-L). as it is among the usual prescriptions and supplements that trainers use.

A 2013 report issued by then-medical director of the California Horse Racing Board, Dr. Rick Arthur, concluded the use of levothyroxine was worrisome because of the studies showing hyperthyroidism “convincingly relevant.” ” in humans with arrhythmias and “functional abnormalities”. However, Arthur also notes that discussions with several veterinarians have shown that “prescribing thyroxine without assessing thyroid levels is consistent with the standard of care prescribing and dispensing thyroxine at clinics Thoroughbred racecourse in Southern California.” He also points out that Baffert says he’s been taking the supplement for more than five years when horses hit other races because he thinks the supplement helps “build” his horses, so Arthur can’t concluded it was a determining factor to the horses. died in Hollywood Park.

During the investigation of the sudden deaths, Baffert said he had stopped taking Thyro-L altogether.

Registration for

Arthur said in the report that levothyroxine in sedentary horses has been shown to be safe, but another study concluded that more research is needed to determine whether it is “a safe treatment in whether the horses are facing physiological challenges such as exercise or pregnancy.”

The Purdue University and UC-Davis study is a step forward in shedding light on the effects of levothyroxine in competition with racehorses.

This study found that levothyroxine treatment was associated with arrhythmias in three of the six horses in the study and in all cases when the horses were given the highest dose. In two of the horses, no arrhythmias were detected before standard exercise testing on the treadmill, appeared during exercise, and then resolved 40 min after practice. In the third horse, the arrhythmia started during exercise and persisted for several hours afterward. The irregular heartbeat corrected itself within 24 h in the third horse.

Because the training regimen took place on the last day the horses were supplemented with levothyroxine, the study did not show an impact on arrhythmias if the horses continued to be supplemented and trained.

For the study, the researchers used three female and three Standardbreded females aged 4 to 9. All of them were conditioned five days per week for six weeks, and blood lactate levels were monitored. to establish uniform fitness levels. Each horse received three levels of levothyroxine treatment – none, 0.1 milligrams/kg or 0.25 mg/kg. Which horse received what level of treatment during each course of treatment was determined at random. The treatments were also packaged by a pharmacist, who prepared coded bags with levothyroxine powder mixed with dextrose powder so it was not known during the study which horses were receiving the supplement levels. any.

The dosage used is two or five times higher than that required to achieve normal serum concentrations. They were chosen because the treatments resulted in thyroxine levels similar to those “found in post-race horse samples with suspected or confirmed atrial fibrillation,” as the Racing Commission veterinarian said. Ontario car has seen. One of the concerns about the use of levothyroxine is that it is not regulated by most horse racing and performance jurisdictions, so there is no way to determine how much supplementation is going on.

Besides the effect on the heart muscle, the study’s conclusion notes that hyperthyroidism is also associated with decreased bone mineral density in humans and an increased risk of fractures.

The study notes: “Skeletal muscle deterioration is a major problem in horse racing and ensuring that horses do not compete if they have high blood levels of thyroid hormone can eliminate hyperthyroidism as a factor. potential contributing factors to catastrophic injury,” the study noted. “Certainly, more research is needed on the effects of iatrongenic levothyroxine use on musculoskeletal health.”

Scene - Gulfstream Park - 010922
Photo: Coglianese Photos



Source link

news7g

News7g: Update the world's latest breaking news online of the day, breaking news, politics, society today, international mainstream news .Updated news 24/7: Entertainment, Sports...at the World everyday world. Hot news, images, video clips that are updated quickly and reliably

Related Articles

Back to top button