What to watch with TSH and longevity?

TSH (thyroid-stimulating hormone) is a key marker of thyroid function. In longevity research, slightly elevated TSH within the upper normal range (e.g., 2.0–4.5 mU/L) has been associated with lower all-cause mortality in older adults. The hypothesis is that reduced thyroid activity slows metabolism and decreases oxidative stress. However, evidence is moderate and comes mainly from observational studies (e.g., PMID: 27179263). Importantly, an isolated high TSH without free T3/T4 measurement and clinical symptoms is not a reliable longevity predictor. Subclinical hypothyroidism (TSH >4.5 mU/L) may increase cardiovascular risk. For individual assessment, free T3, free T4, thyroid antibodies, and clinical context are essential. DNA tests for TSH-related genes (e.g., PDE8B, CAPZB) provide only weak hints and cannot replace blood work. Conclusion: TSH alone is not a longevity marker; interpretation requires medical guidance and a full thyroid profile.