Graves' Disease: A High-Yield USMLE Review

Graves' disease is an autoimmune disorder and the prototypical cause of hyperthyroidism, driven by antibodies that continuously stimulate the TSH receptor. It is high-yield because it is the only cause of hyperthyroidism associated with ophthalmopathy and because its diagnostic (high RAIU, positive TSI) and management pathways are heavily tested. Recognizing exophthalmos as the key differentiator from other causes of thyrotoxicosis is a classic exam point.

Presentation

• Hyperthyroidism with a diffuse goiter: heat intolerance, palpitations, tremor, and unintentional weight loss with increased appetite
• Anxiety, irritability, insomnia, tachycardia, and warm, moist skin; atrial fibrillation may occur
• Ophthalmopathy — proptosis (exophthalmos), lid lag/lid retraction, and diplopia — the finding specific to Graves'
• Dermopathy (pretibial myxedema), which is rare
• Not all patients have the full triad of hyperthyroidism, ophthalmopathy, and dermopathy

Diagnosis

• TSH and Free T4/T3: suppressed TSH with elevated Free T4 and T3 confirms hyperthyroidism
• TSI (thyroid-stimulating immunoglobulin) or TRAb (TSH receptor antibodies): positive, confirming the autoimmune etiology
• Radioactive iodine uptake (RAIU): diffusely increased, reflecting active overproduction; not always necessary when the clinical picture (e.g., ophthalmopathy) is classic

Management

• Antithyroid drugs (methimazole, or PTU in the first trimester of pregnancy): preferred for mild disease, young patients with small goiter, and pregnancy; Graves' can uniquely be managed medically long-term
• Radioactive iodine ablation: preferred for moderate–severe disease without significant ophthalmopathy, relapse after antithyroid drugs, and older or cardiac patients; render the patient euthyroid first
• Surgery (thyroidectomy): preferred for large goiter with compressive symptoms, coexisting suspicious nodule, severe ophthalmopathy, or when medications/I-131 are not options
• Beta-blockers (e.g., propranolol) for symptomatic relief of tachycardia and tremor

High-yield

• Graves' is the only cause of hyperthyroidism associated with ophthalmopathy — exophthalmos is the key differentiator from toxic multinodular goiter and thyroiditis
• TSI/TRAb activate the TSH receptor without feedback regulation — the mechanism of unregulated stimulation
• High RAIU (diffusely increased) points to overproduction (Graves', toxic nodule) whereas low RAIU indicates destruction/exogenous hormone (thyroiditis)
• In pregnancy, use PTU in the first trimester (methimazole causes embryopathy — aplasia cutis, choanal/esophageal atresia) and switch to methimazole thereafter (PTU has higher hepatotoxicity)
• Graves' antibodies cross the placenta, so the fetus requires monitoring for thyrotoxicosis

Pitfalls

• Confusing Graves' with other hyperthyroid states: toxic multinodular goiter and thyroiditis lack ophthalmopathy; thyroiditis (postpartum, subacute) shows LOW RAIU and should not be treated with antithyroid drugs
• Giving radioactive iodine before rendering the patient euthyroid, or using it in pregnancy (contraindicated) or in patients with severe ophthalmopathy (may worsen eye disease)
• Continuing methimazole in the first trimester rather than switching to PTU, exposing the fetus to methimazole embryopathy
• Treating with a beta-blocker alone, which controls symptoms but does not address the underlying hyperthyroidism