Hyperthyroidism
An overactive thyroid producing excess hormone, causing weight loss, tremor and palpitations.
Overview
Hyperthyroidism is most often caused by Graves' disease. Treatment options include antithyroid drugs (carbimazole), radioiodine and surgery. Beta-blockers help symptoms while underlying treatment takes effect.
Symptoms
- • Weight loss with normal appetite
- • Heat intolerance
- • Tremor
- • Palpitations
- • Anxiety
- • Diarrhoea
- • Eye changes (Graves')
Risk factors
- • Female sex
- • Family history of autoimmunity
- • Recent pregnancy
- • Smoking (worsens eye disease)
Causes
- • Graves' disease
- • Toxic nodular goitre
- • Thyroiditis
- • Excess iodine or levothyroxine
🚨 Red flags — seek urgent care
- • Fever, agitation and very high heart rate (thyroid storm)
- • New irregular heartbeat
When to seek care
- • Persistent palpitations or weight loss
- • Eye pain or vision change
Diagnosis
- • Suppressed TSH with raised free T4 and/or T3
- • TSH-receptor antibodies (TRAb) to confirm Graves; thyroid uptake scan to differentiate Graves vs toxic nodule vs thyroiditis
- • Assess eye signs (Graves orbitopathy), goitre and atrial fibrillation
Treatment
- • Antithyroid drugs: carbimazole (or propylthiouracil in first-trimester pregnancy) — titration regimen or block-and-replace for 12–18 months
- • Beta-blocker (propranolol) for symptom control
- • Radioactive iodine therapy — definitive in most non-pregnant adults
- • Thyroidectomy for large goitre, severe orbitopathy, or pregnancy where RAI contraindicated
- • Monitor for hypothyroidism after definitive treatment
Prevention
- • No primary prevention
- • Smoking cessation reduces Graves orbitopathy risk
- • Avoid excessive iodine intake (kelp, amiodarone)
Complications
- • Thyroid storm (medical emergency)
- • Atrial fibrillation and heart failure
- • Osteoporosis from prolonged untreated thyrotoxicosis
- • Graves orbitopathy and vision loss
- • Adverse pregnancy outcomes
Education & self-care
This guidance is reviewed by Dr. Handel Emery, MD, FRCP (UK) and last updated 2026-06-08. It is educational and not a substitute for professional medical advice.
Frequently asked questions
Can hyperthyroidism cause AF?
Yes — uncontrolled hyperthyroidism is a common reversible cause of atrial fibrillation, particularly in older adults.
What are the treatment options?
Anti-thyroid drugs (carbimazole, propylthiouracil), radioactive iodine and surgery. Choice depends on cause (Graves' disease vs nodular), severity, age, pregnancy plans and patient preference.
Can it affect my eyes?
Graves' disease can cause thyroid eye disease — bulging, double vision, dryness. Smoking dramatically worsens it; stopping is the single most important step.
Is it dangerous in pregnancy?
Untreated hyperthyroidism increases miscarriage, preterm birth and pre-eclampsia. Specialist endocrine and obstetric care is essential; propylthiouracil is preferred in the first trimester.