Hyperthyroidism
Overactive thyroid — Graves' disease and medical management
Hyperthyroidism is a condition in which the thyroid gland produces excess thyroid hormone, accelerating the body's metabolism. It affects around 1 in 50 women and 1 in 500 men in the UK. Graves' disease is the most common cause, accounting for approximately 70% of cases.
Causes and types
Graves' disease is an autoimmune condition in which thyroid-stimulating immunoglobulins (TRAb — TSH receptor antibodies) stimulate the thyroid to overproduce hormone. Other causes include toxic multinodular goitre, toxic adenoma, thyroiditis (De Quervain's, postpartum), and excess iodine or thyroid hormone ingestion. TSH is suppressed (<0.1 mIU/L) with elevated free T4 and/or free T3.
Symptoms
Symptoms reflect a hypermetabolic state: weight loss despite normal or increased appetite, heat intolerance, excessive sweating, palpitations, tremor, anxiety, irritability, fatigue, diarrhoea, and oligomenorrhoea. On examination: tachycardia, fine tremor, warm moist skin, and goitre. Graves'-specific features include Graves' ophthalmopathy (proptosis, periorbital oedema, diplopia — occurs in 25–30%) and pretibial myxoedema. Atrial fibrillation develops in around 10–20% of cases, particularly in older patients.
Medical management
Antithyroid drugs (ATDs) are first-line in the UK. Carbimazole 20–40 mg OD is used either as a titration regimen (dose reduced as thyroid function normalises) or block-and-replace (high-dose carbimazole with added levothyroxine). Treatment is typically continued for 12–18 months. Propylthiouracil (PTU) is preferred in the first trimester of pregnancy and in thyroid storm. A beta-blocker (propranolol 40–80 mg TDS) is used to rapidly control adrenergic symptoms while awaiting ATD effect. TFTs are monitored at 4–6 weekly intervals initially.
Definitive treatment
Definitive treatment options after ATD remission include radioiodine (I-131) — the most common definitive treatment; contraindicated in pregnancy and active Graves' ophthalmopathy — and thyroidectomy, preferred for large goitres, co-existing suspicious nodules, or patient preference. Both typically result in hypothyroidism requiring lifelong levothyroxine. Graves' ophthalmopathy requires ophthalmology review and may require selenium supplementation, IV methylprednisolone, or orbital decompression surgery.
Thyroid storm — emergency management
Thyroid storm is a rare but life-threatening complication with mortality up to 20–30%. Precipitants include infection, surgery, or iodinated contrast media. Features: fever >38.5°C, tachycardia, agitation, confusion, and multi-organ failure. Treatment in ITU: propylthiouracil 200 mg 4-hourly (blocks synthesis AND conversion of T4 to T3), Lugol's iodine 0.5 ml 8-hourly (given at least 1 hour after PTU to block hormone release), propranolol IV/oral, dexamethasone 4 mg QDS (reduces T4-to-T3 conversion), and treatment of the precipitating cause. A thorough evaluation of the trigger is essential before discharge.