What should you know about T4 in hyperthyroidism?

T4 is a thyroid hormone that influences energy use, temperature regulation and heart activity. In hyperthyroidism, the thyroid produces too much hormone, and blood tests commonly assess free T4 together with TSH; T3 may add useful information. The pattern can help confirm thyroid overactivity, assess its intensity and guide treatment. Symptoms can include palpitations, excessive sweating, heat intolerance, difficulty sleeping, feeling anxious or diarrhoea, but symptoms alone cannot establish the diagnosis.

Attend the arranged blood test and tell the clinician about thyroid medicines, heart medicines, supplements and pregnancy. Do not alter treatment without advice. Depending on the results, care may involve medicine that reduces thyroid hormone production, medicine that eases symptoms, or referral for a further assessment. Keep a note of palpitations, sleep, bowel changes, sweating and heat sensitivity; these details help show whether treatment is settling the hormone imbalance.

Get urgent help for chest pain, fainting, severe breathlessness, a very fast or irregular heartbeat that does not settle, severe agitation, confusion or a high temperature with rapidly worsening illness. Contact your clinician promptly if symptoms intensify after a treatment change or if you cannot keep medicines down. These situations need assessment rather than interpretation of the T4 result alone.

Ask whether your result is free T4 or total T4; how it fits with TSH and T3; what cause is being considered; when the next test is due; how treatment effects will be monitored; and which heartbeat or heat-related symptoms need urgent help.