Myths vs facts: FT3 and Abnehmen

FT3 (free triiodothyronine) is the active thyroid hormone and is often linked to metabolism. A common myth is that low FT3 directly causes weight gain and that raising FT3 levels (e.g., via supplementation) automatically leads to weight loss. In reality, FT3 is low in overt hypothyroidism and can contribute to a reduced metabolic rate, but in euthyroid individuals (normal thyroid function), FT3 correlates only weakly with weight changes. Supplementing T3 (liothyronine) for weight loss is dangerous and unsupported by randomized controlled trials; it can cause thyrotoxicosis, arrhythmias, and muscle wasting. Another myth: an isolated low FT3 with normal TSH and fT4 (so-called low-T3 syndrome) requires treatment. This often occurs during caloric restriction or illness and is an adaptive response, not a disorder. Evidence shows that FT3 measurements without clinical context (TSH, fT4, symptoms) are not predictive for weight loss. The fact is: balanced nutrition and calorie control are more effective than chasing hormone levels. If thyroid issues are suspected, a physician should be consulted.