Myths vs facts: TSH and Müdigkeit

The claim that a single TSH value directly causes or rules out fatigue is a myth. TSH (thyroid-stimulating hormone) is a screening marker for thyroid function, but fatigue has many causes: iron deficiency, sleep disorders, stress, vitamin D deficiency, or infections. An isolated abnormal TSH without abnormal free thyroid hormones (fT3, fT4) and without clinical symptoms is often not causative. Fact: Overt hypothyroidism (low fT4, high TSH) can cause fatigue, as can hyperthyroidism. However, individual responses vary; so-called 'subclinical' cases (slightly elevated TSH, normal fT4) do not always produce symptoms. Evidence from general medicine and endocrinology is moderate: TSH is a screening test, not a standalone fatigue marker. Without specific studies in the provided context, the evidence is limited. Caveat: No direct sources in context; answer based on general medical knowledge.