What is the most common cause of hyperthyroidism?

The thyroid uses hormones to influence heart rate, temperature control, digestion and energy use. In Graves disease, antibodies act like a thyroid-stimulating signal, so the gland remains active when the body does not need extra hormone. Symptoms can include palpitations, feeling anxious, difficulty sleeping, excessive sweating, heat intolerance or diarrhoea. A symptom does not by itself identify Graves disease; thyroid blood tests and sometimes antibody tests or imaging help clinicians distinguish it from other causes, such as thyroid inflammation, nodules or excess thyroid medicine.

Arrange a clinical assessment if symptoms persist, recur or interfere with daily life. A clinician may check your pulse and neck, review medicines and supplements, and request thyroid-function tests. Do not change prescribed thyroid treatment without advice. Keep a note of racing-heart episodes, heat sensitivity, bowel changes and sleep problems, including when they occur. Treatment depends on the cause and may involve medicine, monitoring or specialist care.

Seek urgent medical help for chest pain, severe breathlessness, fainting, confusion, a very fast or irregular heartbeat, or a high fever with marked agitation. These symptoms can signal a serious effect of excess thyroid hormone or another emergency. Prompt assessment is also sensible when palpitations are new or worsening.

Ask whether your results suggest Graves disease or another cause, which tests are needed, whether any medicine or supplement could be contributing, and how to monitor your heart rate and symptoms.