Penyakit Graves

01Pathophysiology

Graves disease is an autoimmune disorder in which B lymphocytes produce thyroid-stimulating immunoglobulin (TSI), an autoantibody directed against the TSH receptor on thyroid follicular cells. Unlike TSH itself, TSI is not subject to negative feedback from circulating thyroid hormones. The result is continuous, unregulated stimulation of the thyroid gland, leading to excessive synthesis and secretion of T3 and T4.

Because TSI activates the same receptor as TSH, the entire gland is stimulated uniformly. This explains the diffusely enlarged, hyperactive thyroid seen on exam and the diffusely increased uptake on radioactive iodine scanning. The gland becomes hypervascular due to increased metabolic demand, producing the characteristic thyroid bruit on auscultation. This bruit is a key discriminator: a nodular goiter (as in toxic multinodular goiter or Plummer disease) does not produce a diffuse bruit in the same way.

The systemic effects of thyrotoxicosis result from excess thyroid hormone acting on nearly every organ system. T3 increases basal metabolic rate (weight loss, heat intolerance), upregulates beta-adrenergic receptors in the heart (tachycardia, palpitations, risk of atrial fibrillation), increases gut motility (frequent stools), and accelerates bone turnover. The hyperdynamic cardiovascular state is the reason beta-blockers are first-line symptomatic therapy.

Graves ophthalmopathy is distinct from the thyrotoxicosis itself. TSH receptors are also expressed on orbital fibroblasts and adipocytes. TSI-mediated activation of these cells triggers an inflammatory cascade with glycosaminoglycan deposition and edema within the extraocular muscles and retro-orbital fat. The resulting increase in orbital volume pushes the globe forward, causing proptosis. This process is independent of thyroid hormone levels, which is why ophthalmopathy can worsen even after the patient becomes euthyroid or hypothyroid.

Pretibial myxedema follows a similar mechanism: TSH receptor-bearing fibroblasts in the dermis of the pretibial region are activated by TSI, causing localized glycosaminoglycan accumulation. The resulting skin changes are thickened, waxy, nonpitting plaques over the anterior shins. This finding is essentially pathognomonic for Graves disease.

02Classification and Clinical Manifestation

Thyrotoxicosis Severity

Graves Ophthalmopathy Classification (Werner / NO SPECS)

Eponymous Signs in Graves Ophthalmopathy

The most commonly tested eponymous signs in a clinical exam setting are Von Graefe sign (lid lag), Dalrymple sign (lid retraction), and Mobius sign (convergence failure). Von Graefe sign is particularly high-yield because it is often described in vignettes as "the patient's upper eyelid does not follow the globe on looking downward."

Other Manifestations

03Diagnostic Workup

TSH is always the first test ordered when hyperthyroidism is suspected. A suppressed TSH prompts measurement of free T4 (and free T3 if free T4 is normal but clinical suspicion remains high). If both TSH suppression and elevated free T4 confirm thyrotoxicosis, the next question becomes: what is the cause?

This is where TSI (or TRAb) and RAIU become critical. TSI is the most useful serologic test because a positive result is essentially diagnostic of Graves disease and eliminates the need for a nuclear scan in many clinical settings. However, RAIU remains the gold standard imaging test for differentiating Graves from other causes of thyrotoxicosis. The expected pattern in Graves is diffusely elevated uptake across the entire gland.

RAIU Differential

This RAIU pattern table is one of the highest-yield items in thyroid testing. The critical teaching point: low or absent RAIU in a thyrotoxic patient means the thyroid is not actively making new hormone. The hormone is either leaking from an inflamed gland (thyroiditis) or being taken exogenously.

In pregnant patients, RAIU is absolutely contraindicated (radioactive iodine crosses the placenta). The workup relies on TSI/TRAb for diagnosis. Thyroid ultrasound with Doppler showing increased vascularity ("thyroid inferno" pattern) can also support the diagnosis noninvasively.

04Management and Treatment

Methimazole is the preferred antithyroid drug in nearly all cases because of its once-daily dosing, faster onset of action, and lower risk of hepatotoxicity compared to PTU. The one exception is the first trimester of pregnancy, where methimazole is avoided due to its association with aplasia cutis and embryopathy (choanal atresia, esophageal atresia). PTU is used during this window and then switched to methimazole after the first trimester.

A key adverse effect of both antithyroid drugs is agranulocytosis (absolute neutrophil count below 500). This occurs in roughly 0.2 to 0.5% of patients and typically presents with sudden high fever and severe pharyngitis. Patients must be instructed to stop the medication immediately and present for an urgent complete blood count if they develop fever or sore throat. This counseling point is frequently tested.

PTU carries an additional risk of hepatic necrosis (potentially fatal), which is the primary reason it is not first-line outside of early pregnancy and thyroid storm.

Radioactive iodine (I-131) is the most commonly used definitive therapy in the United States. It ablates the hyperactive thyroid tissue, and most patients develop permanent hypothyroidism within 6 to 12 months, requiring lifelong levothyroxine replacement. The critical contraindication to remember is moderate-to-severe active Graves ophthalmopathy: RAI can worsen eye disease because the destruction of thyroid tissue releases TSH receptor antigens, amplifying the autoimmune orbital inflammation. If RAI is chosen in a patient with mild ophthalmopathy, concurrent glucocorticoid prophylaxis (prednisone 0.3 to 0.5 mg/kg/day, tapered over 2 to 3 months) is recommended.

Thyroid storm management follows a strict sequence. The order matters:

1. PTU first (blocks new hormone synthesis and peripheral T4-to-T3 conversion)

2. Iodine (potassium iodide or Lugol solution) given at least 1 hour after PTU. The delay is critical: if iodine is given before the thionamide has blocked organification, the iodine load can paradoxically fuel new hormone synthesis (Jod-Basedow phenomenon). Once organification is blocked, excess iodine acutely inhibits hormone release via the Wolff-Chaikoff effect

3. Beta-blocker (propranolol IV or esmolol if hemodynamically unstable)

4. Glucocorticoids (hydrocortisone 100 mg IV every 8 hours) to block peripheral T4-to-T3 conversion and to treat possible concurrent adrenal insufficiency

5. Supportive care: cooling blankets (avoid aspirin as an antipyretic because it displaces T4 from thyroid-binding globulin, increasing free hormone levels), IV fluids, ICU monitoring

05Differential Diagnosis and Distractors

The single most tested discrimination is between Graves and subacute thyroiditis: both can present with thyrotoxicosis, but the presence of thyroid tenderness and a low RAIU points firmly toward thyroiditis. Graves has a nontender goiter with a bruit and a high RAIU.

06Traps and High-Yield Pearls

The most common way students lose points on Graves disease questions involves the RAIU interpretation. A thyrotoxic patient with low or absent RAIU is not Graves, regardless of how textbook the other symptoms appear. Test-writers exploit this by describing a patient with weight loss, tremor, and tachycardia but then revealing a near-zero uptake scan, expecting you to pivot away from Graves toward thyroiditis or factitious intake.

A second frequent trap is the sequence of treatment in thyroid storm. Students often select iodine as the first intervention because they recall the Wolff-Chaikoff effect. However, iodine must never be given before a thionamide has blocked organification. The tested principle: PTU first, iodine at least one hour later.

The ophthalmopathy and RAI interaction is another high-yield trap. A patient with moderate-to-severe active Graves ophthalmopathy is not a candidate for radioactive iodine ablation without glucocorticoid cover, and in truly severe cases, RAI should be avoided altogether in favor of surgery. Vignettes may describe worsening proptosis after RAI treatment, and the expected answer is that this was a predictable consequence of RAI in active eye disease.

Students also confuse methimazole teratogenicity with a blanket contraindication in pregnancy. The nuance is trimester-dependent: PTU in the first trimester, then switch to methimazole for the remainder of pregnancy. If a vignette places a pregnant patient in the second or third trimester, methimazole is the correct answer.

Finally, remember the agranulocytosis counseling point. If a patient on methimazole or PTU develops sudden fever and sore throat, the next best step is to stop the drug and check a CBC with differential immediately. Do not restart the same agent. This clinical scenario is a classic "next best step" question format.

The core competency being tested across Graves disease questions is your ability to integrate the pathophysiology (TSI-driven receptor activation) with the diagnostic workup (RAIU patterns), distinguish it from its look-alikes using one or two discriminating features, and sequence the management correctly in both routine and emergent settings.