What does a high TSH result mean?

A high TSH (thyroid-stimulating hormone) level typically indicates an underactive thyroid (hypothyroidism). The pituitary gland increases TSH secretion to stimulate the thyroid to produce more T4/T3. In primary hypothyroidism, TSH is elevated while free T4 is low; subclinical hypothyroidism shows elevated TSH with normal fT4. Interpretation requires additional markers (fT4, fT3, thyroid antibodies) and clinical context. Factors like stress, sleep deprivation, medications (biotin, glucocorticoids), or non-thyroidal illness can affect TSH. The provided knowledge context does not include specific information on TSH. Therefore, this answer is based on general medical consensus. Evidence strength: strong (clinical guidelines). Caveat: A single TSH value is not diagnostic; medical follow-up is essential. When using consumer lab tests, be aware of methodological limitations and reference range differences.