Everything You Need to Know About Hyperthyroidism (Graves disease) for Step 1

Hyperthyroidism is one of those Step 1 staples that shows up everywhere: tachycardia in a vignette, “exophthalmos” in an image, suppressed TSH on labs, or a postpartum patient with palpitations. The key is to quickly recognize Graves disease as the prototypical cause, then pivot to mechanism → symptoms → labs → next diagnostic step → treatment. This post is a high-yield, Graves-focused deep dive with Step-style patterns and First Aid tie-ins.

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Big Picture: What Is Graves Disease?

Graves disease is an autoimmune hyperthyroidism caused by IgG antibodies that stimulate the TSH receptor, leading to increased synthesis and release of thyroid hormone.

High-yield definition

• Type II hypersensitivity (antibody-mediated receptor stimulation)
• TSH receptor–stimulating antibodies = thyroid-stimulating immunoglobulins (TSI) / TSH receptor antibodies (TRAb)
• Results in diffuse thyroid hyperplasia and increased $T_3/T_4$

First Aid cross-reference: Endocrine → Thyroid disorders → Hyperthyroidism (Graves), TSI, ophthalmopathy, pretibial myxedema.

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Pathophysiology (Step 1-Level Mechanism)

1) Why the thyroid is overactive

• TSI binds and activates TSH receptor on thyroid follicular cells
  → increased iodine uptake
  → increased thyroglobulin iodination
  → increased coupling (MIT/DIT)
  → increased release of $T_3$ and $T_4$
• Pituitary responds appropriately: TSH decreases via negative feedback.

Labs (classic Graves)

• $\uparrow T_3/T_4$
• $\downarrow$ TSH
• $\uparrow$ radioactive iodine uptake (RAIU) with diffuse uptake

2) Why the eyes and skin are involved (uniquely Graves)

These are not due to thyroid hormone excess directly.

Graves ophthalmopathy

• Autoimmune activation of fibroblasts in orbit (TSH receptor expression on fibroblasts)
• GAG deposition + edema + lymphocytic infiltration
  → proptosis, periorbital edema, diplopia

Pretibial myxedema

• Similar mechanism in skin (shins): dermal fibroblasts → GAG deposition
• Produces nonpitting thickened skin

High-yield distinction

• Exophthalmos + pretibial myxedema are specific for Graves among hyperthyroid etiologies.

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Clinical Presentation: Recognize the Pattern Fast

General hyperthyroid symptoms (increased sympathetic activity + hypermetabolism)

Think: “Fast, hot, hyper”

• Heat intolerance
• Sweating
• Weight loss despite increased appetite
• Anxiety/irritability
• Insomnia
• Tremor
• Palpitations
• Hyperreflexia
• Increased bowel movements/diarrhea
• Proximal muscle weakness (thyrotoxic myopathy)

Cardiovascular (very testable)

• Sinus tachycardia
• Atrial fibrillation (especially older patients)
• Widened pulse pressure (increased CO, decreased SVR)

Graves-specific findings

• Diffuse goiter (often with bruit from increased vascularity)
• Ophthalmopathy: proptosis, lid lag, diplopia
• Pretibial myxedema (nonpitting, “orange peel” texture)

Reproductive/bone

• Oligomenorrhea/amenorrhea
• Decreased bone density/osteoporosis (chronic hyperthyroidism increases bone turnover)

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Diagnosis: The Stepwise Approach

Step 1: Confirm hyperthyroidism biochemically

Order:

• TSH (best screening test)
• Free $T_4$ (and sometimes total $T_3$)

Typical Graves labs

• Low TSH
• High free $T_4$ (± high $T_3$)

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High-yield pearl: Some patients have $T_3$ toxicosis (elevated $T_3$ with normal/near-normal $T_4$), especially early Graves.

Step 2: Identify the cause

If hyperthyroidism confirmed:

• TSI/TRAb antibodies (supports Graves)
• RAIU scan if etiology unclear (not in pregnancy)

RAIU patterns (must-know table)

Special situations

• Pregnancy: avoid radioactive iodine. Use TSI/TRAb + clinical/lab assessment; ultrasound can help evaluate nodules/goiter.
• Subacute thyroiditis: painful thyroid + elevated ESR/CRP + transient hyperthyroidism; low RAIU.

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Treatment: What to Do, When, and Why (Step 1 + Step 2)

Management depends on severity, patient factors (pregnancy, age), and whether you want symptom control, short-term hormone suppression, or definitive therapy.

1) Immediate symptom control: beta-blockers

• Propranolol (nonselective) is classic because it also decreases peripheral conversion of $T_4 \to T_3$ at higher doses.
• Atenolol/metoprolol also commonly used (especially if asthma/COPD considerations; though cardioselective is preferred).

Use for:

• Tremor, palpitations, anxiety, tachycardia
• Bridge while waiting for antithyroid meds to work

2) Antithyroid drugs (reduce hormone synthesis)

Methimazole (MMI) and propylthiouracil (PTU) inhibit thyroid peroxidase, blocking:

• organification (iodination)
• coupling (MIT/DIT → $T_3/T_4$)

PTU also inhibits peripheral conversion of $T_4 \to T_3$.

Choosing MMI vs PTU (high yield)

• Methimazole: preferred for most patients (more effective, longer half-life, less hepatotoxicity)
• PTU: preferred in
  • 1st trimester pregnancy (methimazole is teratogenic)
  • thyroid storm (extra $T_4 \to T_3$ blockade)

Adverse effects to memorize

• Agranulocytosis (both): fever + sore throat → stop drug and check ANC
• Hepatotoxicity: PTU > MMI (PTU can cause severe liver failure)
• Methimazole teratogenicity: classically aplasia cutis, choanal/esophageal atresia

First Aid cross-reference: Thyroid pharmacology—thioamides, PTU in pregnancy and thyroid storm; agranulocytosis warning.

3) Definitive therapy

Radioactive iodine ablation (I-131)

• Causes destruction of thyroid tissue
• Often results in hypothyroidism → requires levothyroxine replacement

Contraindicated in:

• Pregnancy (and typically avoided during breastfeeding)

Surgery (thyroidectomy)

Consider if:

• Large goiter causing compressive symptoms
• Suspicion for malignancy
• Severe disease not controlled with meds
• Patient can’t receive radioactive iodine (e.g., pregnancy + intolerance to meds)

Pre-op prep (classic Step point)

• Beta-blocker + thioamide, then iodine solution (e.g., potassium iodide/Lugol) shortly before surgery to reduce vascularity and hormone release.

4) Iodine: timing matters

Iodide acutely inhibits thyroid hormone release (Wolff–Chaikoff effect) and decreases gland vascularity.

High-yield rule:

• Give iodine after a thioamide (to avoid providing substrate for new hormone synthesis).

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Thyroid Storm: The “Don’t Miss” Emergency

Thyroid storm = life-threatening hyperthyroidism with systemic decompensation.

Clues in a vignette

• High fever, severe tachycardia, agitation/delirium, vomiting/diarrhea
• Precipitated by surgery, infection, trauma, or stopping antithyroid meds

Treatment (order-friendly framework)

1. Beta-blocker (propranolol or esmolol)
2. PTU (preferred) or methimazole
3. Iodine (after thioamide)
4. Glucocorticoids (decrease peripheral conversion; treat possible adrenal insufficiency)
5. Supportive care (cooling, fluids) + treat trigger (e.g., antibiotics)

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High-Yield Associations & “Vignette Traps”

Autoimmune associations

Graves commonly travels with other autoimmune diseases:

• Type 1 diabetes
• Addison disease
• Pernicious anemia
• Celiac disease
• (Also consider autoimmune polyglandular syndromes)

Postpartum pearls

• Postpartum thyroiditis can cause transient hyperthyroidism but is low RAIU and often followed by hypothyroid phase.
• Graves can also present postpartum—distinguish with TSI and RAIU (if not breastfeeding).

Factitious hyperthyroidism vs Graves

• Factitious: low thyroglobulin, low RAIU, no goiter
• Graves: high RAIU (diffuse), goiter, TSI positive

Eye findings nuance

• Lid lag/stare can be seen in hyperthyroidism generally (sympathetic overactivity).
• True proptosis/exophthalmos is a Graves-specific autoimmune phenomenon.

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Rapid Review (What You Should Be Able to Blurt Out on Test Day)

• Graves = Type II HS; TSI/TRAb stimulates TSH receptor
• Symptoms: heat intolerance, weight loss, diarrhea, tremor, anxiety, tachycardia/A-fib
• Exam: diffuse goiter + bruit, ophthalmopathy, pretibial myxedema
• Labs: $\downarrow$ TSH, $\uparrow$ $T_3/T_4$
• RAIU: high, diffuse (vs thyroiditis = low)
• Treatment:
  • Beta-blocker for symptoms
  • Methimazole usually; PTU in 1st trimester and thyroid storm
  • Definitive: radioiodine (not pregnancy) or thyroidectomy
• Thyroid storm: beta-blocker + PTU + iodine + steroids