Evidence check: TCF7L2 in the context of Müdigkeit

TCF7L2 is a transcription factor central to Wnt signaling. Multiple GWAS (e.g., PMID 17463246, 17463248) have firmly linked variants in this gene to increased risk of type 2 diabetes. Fatigue is not a direct outcome of TCF7L2 variation. However, undiagnosed or poorly managed diabetes can cause fatigue, creating an indirect but clinically relevant link. A consumer DNA test reporting TCF7L2 variants provides a risk indicator, not a diagnosis. Effect sizes are moderate, and lifestyle factors (diet, exercise, stress) play a larger role. Persistent fatigue warrants medical evaluation including blood glucose and HbA1c. The evidence for a direct TCF7L2–fatigue connection is weak; strong evidence exists only for diabetes. Interpretation should be cautious and contextual.