Is FT4 useful for fatigue?

The provided context does not address whether FT4 is useful for fatigue. In general medical practice, FT4 (free thyroxine) is a thyroid hormone test used to diagnose thyroid dysfunction, which can cause fatigue. However, fatigue has many potential causes (e.g., iron deficiency, sleep disorders, stress). Measuring FT4 alone is insufficient; a full clinical evaluation is needed. Evidence: practice/guidelines.