Myths vs facts: FT3 and Sport

FT3 (free triiodothyronine) is the active thyroid hormone and plays a key role in energy metabolism, making it relevant for athletes. A common myth is that higher FT3 levels automatically improve performance. In reality, the relationship is complex: moderate endurance training can slightly lower FT3 as an adaptive response to increased energy turnover, while artificially raising FT3 via supplements or thyroid hormones is not recommended. Excess FT3 can cause arrhythmias, muscle wasting, and overtraining. Another myth is that FT3 deficiency can be corrected by exercise alone – manifest hypothyroidism requires medical treatment. Evidence for performance-enhancing effects of FT3 elevation in healthy athletes is weak, mostly based on mechanistic reasoning rather than controlled trials. Safety note: taking thyroid hormones without medical indication is dangerous and can lead to thyrotoxicosis. Evidence-based approach: focus on balanced nutrition, adequate iodine and selenium, and regular medical check-ups for thyroid issues.