What should you know about high TSH and hyperthyroidism?

TSH is a signal from the pituitary gland that helps regulate thyroid hormone production. In typical hyperthyroidism, thyroid hormone is raised and TSH is low. A result that does not follow that pattern is a reason to review the whole picture rather than label yourself from one test.

High TSH can occur when the thyroid is underactive, but it can also need repeat or more detailed testing. Recent changes in thyroid treatment, missed doses, taking a dose shortly before testing, illness, pregnancy, and medicines or supplements can affect how results are interpreted. Your clinician will usually consider free T4 and sometimes free T3 alongside TSH.

Hyperthyroidism can present with palpitations, heat intolerance, excessive sweating, diarrhoea, feeling anxious, or difficulty sleeping. These symptoms can also have causes outside the thyroid, so symptoms alone cannot confirm the diagnosis.

Arrange a review with the clinician who requested the test. Bring the exact names and doses of thyroid medicine, vitamins, supplements, and other regular medicines. Explain whether your symptoms started before or after a treatment change and whether you have had a recent illness.

Do not start, stop, or alter thyroid medicine on the basis of TSH alone unless your prescriber tells you to. A repeat blood test may be appropriate when the timing of treatment or an unexpected result makes the initial reading hard to interpret.

Seek urgent medical assessment for chest pain, fainting, severe shortness of breath, new confusion, or a fast or irregular heartbeat that does not settle. These symptoms need prompt assessment whether or not they are related to the thyroid.

Contact a clinician promptly if palpitations are new or worsening, if you cannot keep fluids down because of diarrhoea, or if thyroid symptoms are rapidly changing while you take treatment.

Ask which thyroid hormone tests were checked with TSH, whether the sample timing could matter, and whether any medicine or supplement could influence the result. You can also ask what symptom changes should prompt earlier contact and when repeat testing would clarify the pattern.