Hyperthyroidism

Hyperthyroidism means the thyroid is overactive - producing more T4 and/or T3 than the body needs. This excess hormone accelerates many functions, leading to a characteristic set of symptoms.

Common symptoms include a fast or irregular heartbeat (palpitations), weight loss despite normal or increased appetite, feeling hot and sweating more than usual, anxiety, tremor, difficulty sleeping, frequent bowel movements, and fatigue. Some people develop a goitre.

The most common cause in the UK is Graves' disease (autoimmune). Other causes include toxic multinodular goitre, a single toxic adenoma, thyroiditis causing temporary hormone release, and, rarely, excess iodine intake or certain medicines.

Diagnosis is confirmed with blood tests showing a suppressed TSH (often very low or undetectable) with elevated free T4 and/or free T3. Further tests - such as TRAb antibodies or a thyroid scan - help identify the underlying cause and guide the choice of treatment.