Overview
Hyperthyroidism means the thyroid gland produces too much thyroid hormone, accelerating all body processes. The most common cause is Graves disease, an autoimmune condition. Other causes include toxic multinodular goitre and toxic adenoma. The condition is treatable and most people return to normal thyroid function.
How common is it?
An overactive thyroid can affect anyone but is more common in women. Graves' disease is a common cause; other causes include overactive thyroid nodules.
Causes and risk factors
Excess thyroid hormone comes from autoimmune stimulation of the gland, autonomous nodules, or external iodine/drug excess.
Common risk factors
- Graves disease (stimulating TSH-receptor antibodies)
- Toxic multinodular goitre (autonomous nodules producing excess hormone)
- Toxic adenoma (single autonomously functioning nodule)
- Thyroiditis (transient phase of excess hormone release)
- Amiodarone or iodine excess
- TSH-secreting pituitary adenoma (rare)
- Factitious hyperthyroidism (excess thyroxine ingestion)
Symptoms
- Palpitations and rapid heart rate
- Unintentional weight loss despite good appetite
- Heat intolerance and sweating
- Tremor of the hands
- Anxiety, irritability, and restlessness
- Diarrhoea or frequent bowel movements
- Fatigue and muscle weakness
- Menstrual irregularities
- Graves disease: protruding eyes (exophthalmos), goitre, pretibial myxoedema
When to see a doctor
Seek assessment for unexplained weight loss, palpitations or tremor. Fever with a very rapid heartbeat, confusion or collapse may be thyroid storm: call your local emergency number immediately.
Diagnosis
TSH is suppressed (low). Free T4 and/or free T3 are elevated. TSH-receptor antibodies confirm Graves disease. Thyroid isotope scan differentiates Graves from nodular disease. Thyroid ultrasound assesses for nodules.
Treatments
Antithyroid drugs
Carbimazole or propylthiouracil reduce thyroid hormone production. Thyroid blood tests guide treatment; routine monthly blood counts are not recommended without a clinical reason. If taking carbimazole and you develop fever, a sore throat, mouth ulcers or signs of infection, stop it and seek urgent medical advice for a blood count. Yellow skin or eyes, or dark urine, also need urgent advice. Discuss pregnancy plans with your specialist. If you become pregnant, contact the prescriber promptly; do not stop treatment solely because of pregnancy without advice.
Radioiodine (I-131)
Radioiodine reduces thyroid hormone production and often leads to hypothyroidism requiring replacement hormone. It is not suitable during pregnancy or breastfeeding and may be unsuitable with thyroid eye disease. A specialist will explain radiation precautions and pregnancy-planning intervals.
Thyroidectomy
Surgical removal of the thyroid. Preferred if large goitre, compressive symptoms, suspected malignancy, or patient preference. Results in hypothyroidism requiring lifelong thyroxine.
Beta-blockers
Propranolol or atenolol controls symptoms (palpitations, tremor, sweating) rapidly while awaiting definitive treatment, but do not reduce thyroid hormone levels.
Self-care and lifestyle
- Avoid excess iodine (kelp supplements, iodine-containing tonics)
- Protect eyes from wind and dry air if Graves orbitopathy is present
- Wear sunglasses for light sensitivity
- If planning pregnancy, discuss treatment options with an endocrinologist before conception
Prevention
No reliable prevention exists for autoimmune hyperthyroidism. Avoiding excess iodine supplementation reduces risk of iodine-induced hyperthyroidism in susceptible individuals.
Sources for targeted updates
Updated: 24 October 2026. Urgent-care guidance and the specific treatment or self-care statements corrected in this update; further corrections to frequency. This update covers the named sections; a full review of the remaining guide is pending.