Hyperthyroidism
Hyperthyroidism is the clinical syndrome of thyroid hormone excess, produced by a range of causes from Graves disease and autonomously functioning nodules to destructive thyroiditis and exogenous hormone ingestion. Diagnosis begins with a suppressed thyroid-stimulating hormone and elevated free thyroxine, followed by radioactive iodine uptake testing or antibody measurement to identify the cause, and first-line treatment is a beta blocker for symptom control while the underlying cause directs thionamide, radioactive iodine ablation, or thyroidectomy therapy.
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What this article covers
- Overview
A syndrome, not a single disease: hyperthyroidism describes thyroid hormone excess arising from the thyroid gland itself; thyrotoxicosis is the broader term for elevated circulating thyroid hormone…
- Epidemiology
Overall prevalence about 1.3% of the United States population.
- Risk factors
Underlying autoimmune thyroid disease or family history, the dominant risk factor for Graves disease as the cause of hyperthyroidism.
- Pathophysiology
Autoimmune stimulation (Graves disease): TSH receptor antibodies activate the TSH receptor, driving continuous, unregulated hormone synthesis across the entire diffusely enlarged gland.
- Clinical features
Hyperadrenergic and hypermetabolic symptoms common to all causes: palpitations, tachycardia, systolic hypertension, tremor, hyperreflexia, heat intolerance, weight loss despite preserved or increased appetite, and warm, moist skin.
- Differential diagnosis
Graves disease: a diffusely enlarged gland with a bruit, positive TRAb, and often ophthalmopathy or pretibial myxedema, distinguished by elevated diffuse radioactive iodine uptake, unlike autonomous nodules or destructive thyroiditis.
- Diagnosis
The diagnosis of thyrotoxicosis is biochemical: a suppressed TSH with elevated free T4 and/or total or free T3 confirms the syndrome; determining the specific cause then requires either antibody…
- Management
First, start a beta blocker for rapid symptom control regardless of cause, since most patients with thyrotoxicosis benefit from adrenergic symptom reduction while the cause is determined.
- Complications
Thyroid storm: a life-threatening exacerbation with fever, tachyarrhythmia, and altered mental status, typically precipitated by infection, surgery, trauma, or abrupt medication discontinuation.
- Prognosis
Generally favorable with treatment directed at the underlying cause.
- Prevention
Identify the cause before committing to therapy, since treating destructive thyroiditis with a thionamide or radioactive iodine is both ineffective and unnecessary.
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Related articles
- Graves disease
Graves disease is an autoimmune disorder in which thyrotropin receptor antibodies stimulate the thyroid, causing hyperthyroidism, and is the most common cause of thyrotoxicosis in iodine-sufficient regions. Diagnosis rests on a suppressed thyroid-stimulating hormone with elevated free thyroxine and positive thyrotropin receptor antibodies, and first-line treatment is a thionamide, most often methimazole, with radioactive iodine or thyroidectomy reserved for recurrence or patient preference.
- Thyroid storm
Thyroid storm is a rare, life-threatening exaggeration of thyrotoxicosis with multiorgan dysfunction and mortality up to 30%, most often precipitated by discontinuation of antithyroid drugs, infection, surgery, or trauma in a patient with underlying hyperthyroidism. It is a clinical diagnosis treated emergently in the ICU with intravenous beta-blockade, a thionamide (propylthiouracil transitioning to methimazole), potassium iodide given only after the thionamide, and high-dose glucocorticoids.
- Thyroid nodules
A thyroid nodule is a discrete structural lesion within an otherwise normal thyroid gland, found on ultrasound in about 40% of the United States population though palpable in far fewer, and malignant in roughly 5%. Evaluation begins with a thyroid-stimulating hormone (TSH) level and thyroid ultrasonography, and management is surveillance for benign or low-risk nodules, with lobectomy or total thyroidectomy reserved for cytology suspicious for or diagnostic of malignancy.