Evidence check: TSH Schilddrüse in the context of longevity

The question of TSH (thyroid-stimulating hormone) in the context of longevity is nuanced. Observational studies suggest that both low and high TSH levels are associated with increased mortality, particularly in older adults. A mildly elevated TSH (subclinical hypothyroidism) may even be protective in the very old, a phenomenon sometimes called the 'U-shaped curve'. However, evidence is largely observational; no RCT has proven that targeting a specific TSH range extends lifespan. TSH is influenced by age, sex, iodine status, medications, and circadian rhythm. A single TSH measurement without free T3, free T4, and thyroid antibodies provides limited insight. Direct-to-consumer thyroid tests often overclaim clinical utility. For longevity, maintaining thyroid function within a normal range is prudent, but aggressive optimization based on TSH alone is not supported by strong evidence. The evidence level is human-moderate (observational) with caveats about confounding and reverse causation.