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?
Hyperthyroidism affects about 0.5% of the UK population. Graves disease accounts for 60 to 80% of cases and predominantly affects women aged 20 to 50.
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
See a doctor for unexplained weight loss, palpitations, or tremor. A thyroid storm (extreme hyperthyroidism with fever, rapid heart rate, and confusion) is a medical emergency requiring urgent hospitalisation.
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 (preferred in UK) or propylthiouracil block thyroid hormone synthesis. Used for 12 to 18 months aiming for remission. Remission occurs in about 50% of Graves disease cases. Monthly blood count monitoring required (agranulocytosis risk).
Radioiodine (I-131)
Radioactive iodine ablates the thyroid. Effective, definitive, and safe. Results in hypothyroidism requiring lifelong thyroxine replacement in most people. Contraindicated in pregnancy and moderate-to-severe active Graves orbitopathy.
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.