Iodine contrast and hyperthyroidism: what to know

Some scans use contrast to make blood vessels or organs easier to see. In a person whose thyroid is already overactive, has autonomous nodules, or is vulnerable to iodine changes, the extra iodine can alter hormone production. Symptoms may appear after the scan rather than during it. Hyperthyroidism presents with palpitations, excessive sweating, heat intolerance, feeling anxious, difficulty sleeping, diarrhoea, or night sweats in some people; having one of these symptoms does not prove that contrast caused it.

Tell the imaging team about thyroid disease, previous contrast reactions, thyroid medicines, and recent symptoms before the scan. Do not cancel a needed scan or stop prescribed treatment without discussing the risks and alternatives. Follow the discharge advice and record the scan date, product if known, and any new symptoms. Contact the clinician who requested the scan if you develop a racing heartbeat, unusual sweating, tremor, heat intolerance, or bowel changes. The background condition is explained in [Hyperthyroidism](/conditions/hyperthyroidism/).

Seek prompt medical advice for new or worsening palpitations, persistent diarrhoea, severe restlessness, difficulty sleeping, or marked sweating after iodinated contrast. Seek emergency help for chest pain, severe breathlessness, fainting, confusion, or a very fast or irregular heartbeat. A clinician may review your pulse, symptoms, medicines, and thyroid blood tests to decide what happens next.

Ask whether your thyroid history changes the contrast plan, whether testing or monitoring is needed, and which symptoms should trigger an urgent call. Ask when to restart or adjust any medicine only if your clinician has advised a change.