Is TCF7L2 useful for Müdigkeit?

TCF7L2 is a gene strongly associated with type 2 diabetes (T2D) risk in genome-wide association studies (GWAS). Fatigue is a common but non-specific symptom that can occur in many conditions, including undiagnosed or poorly controlled diabetes. However, TCF7L2 is not a direct 'fatigue gene.' The link is indirect: carriers of risk variants have an increased T2D risk, and untreated diabetes can cause fatigue. Still, the predictive value of a single SNP for fatigue is very low. Most consumer DNA tests overstate the clinical relevance of such markers. If fatigue is the main concern, standard medical workups (blood count, thyroid, iron, vitamin D, sleep quality) are far more useful than a genetic test for TCF7L2. The evidence for direct utility in fatigue is weak and based on mechanistic reasoning, not clinical trials.