Hyperthyroidism
Hyperthyroidism is a condition in which the thyroid gland produces too much thyroid hormone, speeding up the body’s metabolism. It can cause weight loss, palpitations, anxiety and heat intolerance.
The most common cause is Graves’ disease, an autoimmune disorder; other causes include toxic nodules, thyroiditis and excessive iodine intake.
Last medically reviewed: 1 November 2025
Key points
- Hyperthyroidism means the thyroid produces too much hormone.
- Graves’ disease is the most common cause.
- Symptoms include palpitations, weight loss, heat intolerance and tremor.
- Treatment options are antithyroid drugs, radioactive iodine and surgery.
What causes hyperthyroidism?
Graves’ disease accounts for the majority of cases. In this autoimmune condition, antibodies called TRAb stimulate the thyroid to overproduce hormone. Toxic multinodular goitre and toxic adenoma — where one or more nodules autonomously produce hormone — are more common in older patients.
Thyroiditis (inflammation causing stored hormone to leak out), excessive iodine from supplements or contrast dye, and rarely pituitary tumours can also cause thyrotoxicosis.
What are the symptoms?
Symptoms often include unintentional weight loss despite increased appetite, rapid or irregular heartbeat, anxiety or irritability, heat intolerance, sweating, tremor, fatigue, frequent bowel movements, and in Graves’ disease, eye changes such as bulging or irritation.
In older adults, hyperthyroidism may present subtly — mainly as an irregular heartbeat or unexplained weight loss — without the classic hyperactive symptoms.
How is it diagnosed?
A suppressed (low) TSH with elevated free T4 or free T3 confirms thyrotoxicosis. TRAb testing helps identify Graves’ disease, and thyroid uptake scanning (where available) distinguishes causes. Ultrasound evaluates nodules or inflammation.
Distinguishing true hormone overproduction from thyroiditis — where the gland leaks hormone temporarily — is important because management differs.
How is it treated?
Treatment options depend on the cause and patient factors: antithyroid medications (methimazole or propylthiouracil) block hormone production; radioactive iodine (RAI) destroys overactive tissue; and thyroidectomy (surgery) removes the gland. Beta-blockers control symptoms such as palpitations and tremor while definitive treatment takes effect.
Graves’ disease can sometimes go into remission after 12–18 months of antithyroid drugs. RAI and surgery often result in hypothyroidism, which is then managed with levothyroxine.
Frequently asked questions
Is hyperthyroidism serious?
Yes, if untreated it can cause atrial fibrillation, osteoporosis, heart failure and thyroid storm — a rare but life-threatening emergency. Early diagnosis and treatment are important.
Which treatment is best — medication, RAI or surgery?
There is no single best option. Antithyroid drugs suit patients wanting to avoid permanent effects; RAI is convenient and effective for most; surgery is preferred for large goitres, compressive symptoms or suspected cancer. The choice is individualised.
Will I become hypothyroid after treatment?
Quite possibly. RAI and surgery frequently lead to an underactive thyroid, which is managed with levothyroxine — a well-understood and easily treated condition.
Can hyperthyroidism affect pregnancy?
Yes. Uncontrolled hyperthyroidism in pregnancy raises risks for both mother and baby, and Graves’ disease can affect the newborn. Thyroid function should be checked and managed carefully before and during pregnancy.
References & further reading
This page is based on established medical knowledge and guidelines from authoritative sources. Always consult a qualified clinician for personal medical advice.
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