Former Olympic and World champion Kirani James returned from a long layoff to claim the 400 meters at the Racers Grand Prix on Saturday, clocking a winning time of 44.35 seconds.
James produced a final burst to beat runner-up Fred Kerley of the United States by 100th of a second at National Stadium in Kingston.
The impressive showing came one day after James announced that he has Graves' disease, an immune system disorder resulting in an overproduction of thyroid hormones.
The 24-year-old James came from behind with about 40 meters remaining to catch Kerley who got off to a fast start.
James said afterward he was "trying to improve my health and preparation day by day. It's just a blessing to be here and competing."
The Grenadian, who won gold and silver at the 2012 and 2016 Olympic Games, had announced in a pre-meet press conference Friday that he was suffering from the disease.
"I found out I had Graves' disease and for people who don't know what that's about, it's a disease that affects your thyroid.
"And when it overacts it affects your hormones, speeds up your metabolism, weight loss, muscle weaknesses, shortness of breath, a lot of symptoms; sometimes it varies. So I had to see doctors and be on medication.
"It's been a long road, so I am just glad to be back. And I just want to thank the Racers Grand Prix for inviting me and giving me an opportunity to come back and open up to see where I am at. I am just happy to be back," he said.
After the race he told reporters, "I am just getting back to racing after a year and some months and trying to stay focused and determined."
Also, Jamaican-based Great Britain runner Zharnel Hughes ran a world leading 9.91 seconds (0.4m/s), his first time under 10.00 seconds to win the men's 100m.
The long-striding Hughes got out off to a good start and held off the American Noah Lyles, who ran a personal best 9.93. Yohan Blake ran a 10.00 seconds for third.
World and Olympic champion Shelly-Ann Fraser-Pryce continued her come back after giving birth to her first child, and ran a season best 11.10 seconds in the 100m.
Grenada's Kirani James, seen competing in 400m athletics event at Hampden Park during the 2014 Commonwealth Games in Glasgow