What role does FT4 play in Müdigkeit?

FT4 (free thyroxine) is a key thyroid hormone that regulates metabolism. Low FT4 levels can indicate hypothyroidism, a condition strongly associated with fatigue, lethargy, and low energy. However, fatigue is multifactorial: even with normal FT4, other causes like sleep deprivation, stress, iron deficiency, or subclinical thyroid dysfunction (elevated TSH with normal FT4) may be present. FT4 alone is insufficient to diagnose thyroid-related fatigue; a full thyroid panel (TSH, FT3, antibodies) is required. The evidence linking low FT4 to fatigue is human-strong, based on clinical hypothyroidism research. The MyBody-X hormone test provides a single-time-point snapshot useful for screening, not diagnosis. Caveat: do not self-treat; consult a physician for persistent fatigue.