Evidence check: FT4 in the context of Haut

The question about FT4 (free thyroxine) in the context of skin is relevant because thyroid hormones affect skin physiology. Hypothyroidism often causes dry, rough skin, while hyperthyroidism leads to moist, warm skin and increased sweating. However, FT4 alone is not a specific skin biomarker. Evidence comes mainly from observational studies and clinical experience – no randomized trials directly link FT4 to skin aging or health. FT4 levels fluctuate diurnally and can be influenced by medications, inflammation, or assay methods. A consumer blood test may provide a rough indication but does not replace medical evaluation for skin issues. Caution: a single FT4 value without TSH and clinical symptoms has limited interpretability. Evidence: human-moderate (observational).