welche werte bei schilddrüsenunterfunktion — which blood markers matter?

The key blood markers for hypothyroidism (underactive thyroid) are TSH (thyroid-stimulating hormone), free T4 (fT4), and free T3 (fT3). An elevated TSH with normal or low fT4 indicates subclinical hypothyroidism; elevated TSH with low fT4 confirms overt hypothyroidism. fT3 is less reliable for diagnosis as it often remains normal until late stages. Autoantibodies against thyroid peroxidase (TPO-Ab) and thyroglobulin (Tg-Ab) help identify Hashimoto's thyroiditis as the underlying cause. Reference ranges vary by laboratory, age, and comorbidities. Important caveat: In secondary (central) hypothyroidism due to pituitary disease, TSH may be low or inappropriately normal despite low fT4. Therefore, clinical context is essential. These markers are well-established in clinical guidelines (evidence: human-strong). However, no single test is perfect; diagnosis requires integration of symptoms (fatigue, weight gain, cold intolerance) and lab results. Always consult a physician for interpretation and treatment decisions. Note: The provided context did not contain specific thyroid information; this answer is based on standard medical knowledge.