PassFinals
Endocrinology & Metabolic

Hyperthyroidism

A state of thyroid hormone excess that accelerates metabolic rate across almost every tissue, so the clinical picture (weight loss despite hunger, heat intolerance, tachycardia and tremor) can be derived directly from asking what a sped-up metabolism looks like.

In a nutshell

Thyroid hormone excess accelerates metabolism: weight loss despite hunger, heat intolerance, tremor, tachycardia or atrial fibrillation. Confirm thyrotoxicosis biochemically, distinguish Graves' or toxic nodular hyperthyroidism from thyroiditis, control symptoms, then choose antithyroid drugs, radioactive iodine or surgery according to cause, eye disease, pregnancy and patient priorities.

Classic presentation

A younger woman with weight loss despite increased appetite, heat intolerance, palpitations, tremor and a diffuse goitre, sometimes with eye signs.

Key points

  • TSH is suppressed in primary hyperthyroidism because excess T4/T3 feeds back on the pituitary; a low TSH with raised T4/T3 confirms it.
  • Graves' disease is caused by TSH-receptor stimulating antibodies, which is why it uniquely produces thyroid eye disease and pretibial myxoedema.
  • Measure TRAb to confirm Graves' disease; if TRAb is negative, consider technetium scanning. Diffuse uptake supports Graves', focal or patchy uptake nodular disease, and low uptake thyroiditis.
  • Beta-blockers control adrenergic symptoms quickly but do not treat the underlying hormone excess: a thionamide or definitive treatment is still needed.
  • Thyroid storm is an exaggeration of the same physiology, precipitated by infection, surgery, iodine load or drug withdrawal, and is a monitored emergency requiring combined treatment.
  • Agranulocytosis is a rare but serious side effect of thionamides: sore throat or fever warrants an urgent full blood count.
  • Carbimazole carries MHRA warnings for congenital malformations if taken in early pregnancy (effective contraception should be advised) and for rare acute pancreatitis (stop immediately and permanently if this occurs).

First-line investigation

TSH and free T4/T3 to confirm the diagnosis, followed by TSH receptor antibodies or an uptake scan to establish the cause.

Management

Recognise danger and control symptoms

  • Fever, marked tachycardia or arrhythmia, agitation or delirium, heart failure, hypotension or rapid deterioration suggests thyroid storm: admit urgently to a monitored setting, involve endocrinology and critical care, and treat the precipitant.2,3
  • Use a beta-blocker for tremor, palpitations and tachycardia when clinically appropriate, but remember it controls peripheral adrenergic effects and does not reduce thyroid hormone production. Use supportive treatment alone when the picture is transient thyrotoxicosis without hyperthyroidism.1,4

Confirm the cause before choosing a long-term pathway

  • For suspected primary thyroid dysfunction, measure TSH first when pituitary disease is not suspected, then FT4 and FT3 if TSH is below the reference range. Measure TRAb to confirm Graves' disease; if negative, consider technetium scanning. Do not routinely use ultrasound unless a palpable nodule is present.1
  • Before an antithyroid drug, check full blood count and liver function. For selected adult Graves' disease, carbimazole is offered for 12 to 18 months using a titration or block-and-replace regimen; do not use antithyroid drugs to treat thyroiditis without hyperthyroidism.1,4

Protect against medicine and pregnancy harm

  • Fever or sore throat while taking an antithyroid drug requires the drug to be stopped and an urgent full blood count; do not restart any antithyroid drug if agranulocytosis is confirmed. Do not routinely monitor full blood count or liver function without clinical suspicion.1
  • Use effective contraception during carbimazole treatment and arrange prompt endocrine-obstetric review if pregnancy is planned or occurs. Consider propylthiouracil when pregnant or trying to conceive within 6 months; UK pregnancy guidance favours it in the first trimester. Avoid radioactive iodine during pregnancy.1,6,7
  • If acute pancreatitis occurs during carbimazole treatment, stop carbimazole immediately and permanently and use an alternative treatment strategy; never re-expose after carbimazole-associated pancreatitis.5

Choose definitive treatment by cause

  • For adult Graves' disease, offer radioactive iodine as first-line definitive treatment unless an antithyroid-drug course is likely to achieve remission or radioiodine is unsuitable because of pregnancy, near-term fertility plans, compression, suspected malignancy or active thyroid eye disease.1
  • For a single toxic nodule or toxic multinodular disease, offer radioactive iodine if suitable or surgery; consider lifelong titration carbimazole if these options are unsuitable. Use shared decision making about remission, hypothyroidism, eye disease and procedure risks.1
  • For thyroid storm, give combined monitored treatment: beta-blockade when safe, an antithyroid drug, iodine after the antithyroid drug, corticosteroids, cooling, fluid and electrolyte support, and treatment of the precipitant according to the local emergency protocol and BNF.2,3

Monitor relapse, hypothyroidism and eye disease

  • On antithyroid drugs, measure TSH, FT4 and FT3 every 6 weeks until TSH is within range, then TSH with cascading every 3 months until treatment stops. After stopping in adults, check TSH within 8 weeks, every 3 months for a year and then annually.1
  • After radioactive iodine, check thyroid tests every 6 weeks for the first 6 months; after hemithyroidectomy, check TSH and FT4 at 2 and 6 months then annually. Assess thyroid eye disease at every review and urgently refer visual loss, corneal exposure or optic-nerve threat.1
  • Do not treat a single low TSH result as overt disease. For two TSH results below 0.1 mIU/L at least 3 months apart plus symptoms or evidence of thyroid disease, seek specialist advice; if untreated, measure TSH every 6 months.1

Exam traps

  • Low uptake on a radionuclide scan in a hyperthyroid patient suggests thyroiditis (hormone leaking from a damaged gland), not Graves' disease or a toxic adenoma.
  • A sore throat or fever in a patient on carbimazole is agranulocytosis until proven otherwise: stop the drug and check a full blood count urgently.
  • Beta-blockers relieve symptoms but do not lower thyroid hormone levels; do not mistake symptomatic improvement for biochemical control.
  • Carbimazole must not be restarted after an episode of acute pancreatitis linked to the drug: re-exposure risks a faster, more severe recurrence.
  • Radioactive iodine is not a default answer: active thyroid eye disease, pregnancy and near-term fertility plans can make it unsuitable, while toxic nodules follow a different definitive-treatment pathway.
  • A suppressed TSH with normal FT4 and FT3 is subclinical hyperthyroidism; confirm persistence and seek the NICE threshold-based pathway rather than treating one abnormal result as overt disease.

Illustrations

Accelerated metabolism mechanismDiagram mapping thyroid hormone excess to increased metabolic rate and onward to each organ-system feature of hyperthyroidism.PassFinals · original
Graves' ophthalmopathyClinical photograph showing exophthalmos, lid retraction and periorbital swelling characteristic of Graves' thyroid eye disease.Huy A Tran and Glenn EM Reeves, Wikimedia Commons · CC-BY-SA-2.0
Thyroid uptake scan patternsComposite image comparing diffuse uptake in Graves' disease, focal uptake in a toxic adenoma and patchy uptake in multinodular goitre.Petros Perros, Wikimedia Commons · CC-BY-SA-3.0

Key sources

  1. NICE, Thyroid disease: assessment and management (NG145)Published 20 Nov 2019 | Updated 12 Oct 2023
  2. Norfolk and Norwich University Hospitals NHS Foundation Trust, Suspected Thyroid Emergencies Management guideline v3.2 (CA5060 v3.2)
  3. BNF, Propylthiouracil
  4. BNF, Carbimazole
  5. MHRA, Carbimazole: risk of acute pancreatitis (Drug Safety Update)Published 18 Feb 2019
  6. MHRA, Carbimazole: increased risk of congenital malformations; strengthened advice on contraception (Drug Safety Update)Published 18 Feb 2019
  7. NHS England North West, Thyroid disease in pregnancy guideline

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.