What to watch with FT3 and Langlebigkeit?

FT3 (free triiodothyronine) is the active thyroid hormone and plays a key role in energy metabolism. In the context of longevity, an optimal FT3 level is often discussed, but the evidence is complex. Studies indicate that both too low and too high FT3 levels can be associated with increased mortality, especially in older adults. Low FT3 („low T3 syndrome“) frequently occurs in chronic illness and aging and is linked to reduced life expectancy. Conversely, hyperthyroidism (elevated FT3) raises cardiovascular risks. It is crucial not to view FT3 in isolation but together with TSH, fT4, and possibly reverse T3. Genetic variants (e.g., in DIO1/DIO2) can influence T4-to-T3 conversion. Supplementation without medical supervision is risky. The evidence is largely observational; direct causal effects on longevity are not firmly established. Be cautious of marketing claims promoting FT3 as an 'anti-aging hormone.'