What role does FT3 play in Wechseljahre?

The role of free triiodothyronine (FT3) during menopause is not well established by robust evidence. FT3 is the active thyroid hormone that regulates basal metabolic rate, cardiac output, and thermogenesis. During menopause, declining estrogen levels can alter thyroid hormone binding and conversion, potentially affecting FT3 concentrations. However, observational studies show mixed results: some report slight increases or decreases in FT3, while others find no significant change. The provided context lacks direct studies on FT3 and menopause, so the evidence grade is 'unclear'. Mechanistically, estrogen influences thyroid-binding globulin (TBG) and deiodinase activity, but these effects are complex and often confounded by age, BMI, and iodine status. Routine FT3 testing is not recommended for menopausal women without thyroid-related symptoms. If symptoms like fatigue, weight changes, or palpitations occur, TSH should be measured first. FT3 assays have variability and should not be used alone for diagnosis. Clinical assessment and follow-up with a physician are essential. In summary, FT3's role in menopause is plausible but unsupported by strong evidence; caution against overinterpretation is warranted.