Clark Burckle Jr., now 36 years old, is no stranger to adversity. Clark represented the United States in the 2012 Olympics, competing in the 200-meter breaststroke. He’s been a successful entrepreneur with an athletic lifestyle ever since then.

But in 2022, he started feeling unwell. “I had bad fatigue, I lost the desire to work out, I felt very tired and overwhelmed,” he recalls. He noticed a ringing in his left ear – tinnitus...