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Hyperthyroidism and thyrotoxicosis
A low TSH with a high FT4 confirms thyrotoxicosis, but the cause decides the treatment — overproduction (Graves, nodules) is treated with drugs, radioactive iodine or surgery, while inflammation of the gland (thyroiditis) is treated for symptoms only.
Why it matters in the exam
Exam questions present palpitations, weight loss, tremor and heat intolerance, and ask for the next test or the cause. The key is an uptake study or scan: high diffuse uptake — Graves disease; uptake in a single "hot" nodule — toxic adenoma; uptake in several nodules — toxic multinodular goitre; low uptake — thyroiditis (painful and subacute after a viral infection, with a high ESR; painless or postpartum) or hormone taken from outside (low thyroglobulin). Graves disease is also recognised by TRAb antibodies, eye disease and pretibial myxoedema.
Treatment questions focus on side effects and pregnancy. Methimazole is the first drug, except in the first trimester of pregnancy and in thyroid storm, where PTU is preferred. The important side effect of both is agranulocytosis — fever and sore throat call for stopping the drug and an immediate blood count; PTU also causes severe liver injury. Radioactive iodine is contraindicated in pregnancy and breastfeeding and can worsen active eye disease. Thyroid storm is treated with a beta-blocker, an antithyroid drug, iodine (at least an hour after the drug), hydrocortisone, cooling and treatment of the trigger.
Key points
- Low TSH + high FT4 = thyrotoxicosis; uptake separates overproduction from inflammation.
- Graves disease: diffuse uptake, TRAb, eyes; methimazole for 12–18 months.
- PTU in the first trimester and in storm; methimazole otherwise.
- Agranulocytosis: fever and sore throat → stop the drug and check a count.
- Storm: beta-blocker, antithyroid drug, iodine after it, hydrocortisone.
Summary table
| Cause | Scan / tests | Clinical clue | Treatment |
|---|---|---|---|
| Graves disease | High diffuse uptake, positive TRAb | Eye disease, pretibial myxoedema, young woman | Methimazole for 12–18 months; radioactive iodine or surgery |
| Toxic multinodular goitre | Uptake in several nodules | Older patient, arrhythmias | Radioactive iodine or surgery |
| Toxic adenoma | One "hot" nodule, rest of the gland suppressed | Palpable nodule | Radioactive iodine or lobectomy |
| Subacute thyroiditis | Low uptake, high ESR | Painful gland after a viral infection | NSAIDs or steroids, beta-blocker; no antithyroid drugs |
| Exogenous hormone | Low uptake, low thyroglobulin | Small gland, access to medication | Stop the hormone |
| Thyroid storm | Fever, tachycardia, confusion, heart failure | Trigger: surgery, infection, childbirth | Propranolol, PTU or methimazole, iodine, hydrocortisone |
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Sources
- American Thyroid Association Guidelines for Diagnosis and Management of Hyperthyroidism and Other Causes of Thyrotoxicosis, 2016 — Graves disease, toxic nodular goitre, thyroiditis and thyroid storm
- Harrison's Principles of Internal Medicine, 21st edition (2022) — Hyperthyroidism and Other Causes of Thyrotoxicosis
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-02. The text may contain errors; when in doubt, check the source.