What should you know about TSH and T4 levels in hyperthyroidism?

TSH is a signal from the pituitary gland that tells the thyroid how hard to work. T4 is a thyroid hormone measured in the blood. When thyroid hormone is excessive, the pituitary commonly reduces TSH production. A low TSH with raised free T4 supports an overactive thyroid pattern; a low TSH with normal T4 may need further testing, repeat testing, or measurement of T3. Symptoms can include palpitations, heat intolerance, excessive sweating, diarrhoea, difficulty sleeping, or feeling anxious, but they do not establish the cause.

Take the report to a clinician who can review the exact values, reference ranges, medicines, supplements, pregnancy status, and previous results. Do not start, stop, or alter thyroid medicine without advice. Your clinician may arrange repeat thyroid tests, antibody testing, or an examination to clarify whether the pattern reflects [Hyperthyroidism](/conditions/hyperthyroidism/) or another explanation.

Seek urgent help for chest pain, fainting, severe breathlessness, marked confusion, or a very fast or irregular heartbeat. Contact a clinician promptly if palpitations, tremor, sweating, diarrhoea, or heat intolerance are worsening, especially when a thyroid result is abnormal.

Ask whether your TSH and free T4 pattern suggests thyroid overactivity, whether T3 or antibodies are needed, and when the tests should be repeated. Mention biotin and all thyroid medicines because they may affect interpretation.