2.4 Thyrotoxicosis, Thyroid Storm & Thyroid Nodules
Key Takeaways
- Radioiodine uptake separates high-uptake thyrotoxicosis such as Graves disease from low-uptake causes such as thyroiditis and exogenous hormone.
- Painful thyroiditis with low uptake is treated symptomatically with beta-blockade and anti-inflammatory therapy, not with thionamides.
- Thyroid storm is a clinical diagnosis; treatment blocks synthesis, release, peripheral conversion and adrenergic effect, and iodine must follow rather than precede thionamide administration.
- A thyroid nodule with a normal or elevated thyroid-stimulating hormone is evaluated by ultrasound and risk-stratified aspiration rather than by scintigraphy.
- Fine-needle aspiration cytology must be obtained before thyroidectomy because it determines the extent of surgery.
Last updated: August 2026
1. Thyrotoxicosis: Differential Diagnosis & Graves Management
Thyrotoxicosis represents excessive circulating thyroid hormone, whereas hyperthyroidism specifically denotes increased de novo thyroid hormone synthesis by the gland.
Diagnostic Distinction via Radioactive Iodine Uptake (RAIU)
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| RAIU PATTERN | ETIOLOGY & PATHOPHYSIOLOGY | CLINICAL FEATURES & THERAPY |
+------------------------------+----------------------------------------------+-------------------------------+
| HIGH / NORMAL UPTAKE | 1. Graves Disease | - TSI / TRAb positive (>95%) |
| (Active De Novo Synthesis) | - Diffuse homogenous uptake (40-80%) | - Exophthalmos, pretibial |
| | - Autoantibodies stimulate TSH receptor | myxedema, thyroid bruit |
| | 2. Toxic Multinodular Goiter (Plummer) | - Patchy, heterogeneous uptake|
| | - Multiple autonomous hyperactive nodules | - Elderly, compressive goiter |
| | 3. Toxic Adenoma | - Single hot focal nodule with|
| | - Single somatic TSH receptor mutation | suppression of remainder |
+------------------------------+----------------------------------------------+-------------------------------+
| LOW / ABSENT UPTAKE (< 2%) | 1. Subacute Granulomatous Thyroiditis | - Painful, exquisitely tender |
| (Follicular Destruction | (de Quervain / giant-cell thyroiditis) | goiter; elevated ESR/CRP; |
| or Exogenous Source) | - Post-viral inflammatory release | treat with NSAIDs/Steroids |
| | 2. Subacute Lymphocytic (Painless) / | - Non-tender goiter; self- |
| | Postpartum Thyroiditis | limiting; beta-blockers |
| | 3. Exogenous / Factitious Thyrotoxicosis | - Low serum Thyroglobulin; |
| | - Ingestion of thyroid hormone | RAIU < 1% |
| | 4. Struma Ovarii | - Ectopic teratoma; pelvic |
| | - Ovarian teratoma producing T4 | scintigraphy uptake |
+------------------------------+----------------------------------------------+-------------------------------+
Graves Disease Management Modalities
- Antithyroid Drugs (ATDs):
- Methimazole (MMI): Drug of choice for almost all non-pregnant adults and during the 2nd and 3rd trimesters of pregnancy (superior potency, once-daily dosing, lower hepatotoxicity risk than PTU).
- Propylthiouracil (PTU): Preferred ONLY during the 1st trimester of pregnancy (due to MMI teratogenicity: aplasia cutis, choanal atresia) and in Thyroid Storm (due to inhibition of peripheral 5'-deiodinase converting T4 to T3).
- Critical Adverse Effects: Agranulocytosis (absolute neutrophil count < 500/mcL in 0.3–0.5%; presents with sudden fever and severe sore throat -> instruct patients to stop ATD immediately and obtain a stat CBC with differential); Hepatotoxicity (PTU causes fulminant hepatic necrosis; MMI causes cholestatic jaundice); ANCA-associated vasculitis.
- Radioactive Iodine (RAI / I-131 Ablation):
- First-line definitive therapy in the United States. Concentrates in thyroid tissue, inducing cell destruction over 6–18 weeks.
- Absolute Contraindications: Pregnancy and breastfeeding.
- Relative Contraindication: Moderate-to-severe active Graves Orbitopathy (RAI increases TSH receptor antibody titers and worsens ophthalmopathy; administer prophylactic oral Prednisone 0.4–0.5 mg/kg/day if mild orbitopathy undergoing RAI).
- Total Thyroidectomy: Indicated for large compressive goiters, coexisting suspicious malignant nodules, moderate-to-severe active Graves orbitopathy, or patient preference/ATD failure.
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2. Thyroid Storm: Burch-Wartofsky Score & 5-Step Emergency Therapy
Thyroid storm is an acute, life-threatening manifestation of thyrotoxicosis with a mortality rate of 10–30%. It is diagnosed clinically using the Burch-Wartofsky Point Scale (BWPS >=45 is highly suggestive), assessing thermoregulatory dysfunction (fever up to 40°C / 104°F), central nervous system effects (agitation, delirium, psychosis, coma), cardiovascular dysfunction (tachycardia >140 bpm, atrial fibrillation, congestive heart failure), and gastrointestinal-hepatic dysfunction (diarrhea, jaundice, abdominal pain).
5-Step Multimodal Pharmacotherapy Protocol
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| STEP & CLASS | DRUG & DOSAGE | PHYSIOLOGICAL MECHANISM & CRITICAL RULES |
+---------------------+-----------------------------+---------------------------------------------------------+
| 1. Beta-Blocker | Propranolol 60-80 mg PO q4h | Blocks beta-1 and beta-2 adrenergic receptors; |
| | OR Esmolol IV infusion | High-dose propranolol inhibits peripheral 5'-deiodinase |
| | | conversion of T4 to active T3 |
+---------------------+-----------------------------+---------------------------------------------------------+
| 2. Thionamide | PTU 500-1000 mg loading PO, | Blocks de novo thyroid hormone synthesis; PTU also |
| (Antithyroid) | then 250 mg PO q4h | blocks peripheral T4-to-T3 conversion; |
| | (OR Methimazole 20-30 mg q6h| Administer BEFORE inorganic iodine! |
+---------------------+-----------------------------+---------------------------------------------------------+
| 3. Inorganic Iodine | Potassium Iodide (SSKI) | Wolff-Chaikoff effect: acutely blocks thyroid hormone |
| (Iodide block) | 5 drops PO q6h | release from colloid; |
| | OR Lugol Solution 8 drops q6| CRITICAL RULE: MUST WAIT AT LEAST 1 HOUR AFTER |
| | | THIONAMIDE! Giving iodine first fuels hormone synthesis |
| | | (Jod-Basedow phenomenon) and worsens thyroid storm. |
+---------------------+-----------------------------+---------------------------------------------------------+
| 4. Glucocorticoids | Hydrocortisone 100 mg IV q8h| Inhibits peripheral T4-to-T3 conversion; treats relative|
| | OR Dexamethasone 2 mg IV q6h| vasomotor adrenal exhaustion; stabilizes vasomotor tone |
+---------------------+-----------------------------+---------------------------------------------------------+
| 5. Supportive & | Bile acid sequestrants | Cholestyramine (4g PO qID) enhances fecal excretion of |
| Fecal Clearance | (Cholestyramine); | circulating thyroid hormone; Acetaminophen and cooling |
| | Cooling blankets; IV fluids | blankets for fever; AVOID SALICYLATES/ASPIRIN (displaces|
| | | T4/T3 from thyroid-binding globulin, increasing free T4)|
+---------------------+-----------------------------+---------------------------------------------------------+
3. Thyroid Nodules & Malignancy Subtypes
Thyroid Malignancy Classification
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Papillary Thyroid Carcinoma (PTC) (~85% of all thyroid cancers):
- Histopathology: Orphan Annie eye nuclei (cleared, optically empty nuclei), psammoma bodies (laminated calcospherites), nuclear pseudoinclusions, and nuclear grooving.
- Behavior: Spreads via lymphatics to regional cervical lymph nodes; distant metastases rare; excellent 10-year survival rate (>95%).
- Management: Lobectomy (for unifocal tumors <1–4 cm without extrathyroidal extension or nodal involvement) vs Total Thyroidectomy +/- central neck lymph node dissection, followed by postop Radioactive Iodine (RAI) ablation for high-risk features and TSH suppression with levothyroxine.
-
Follicular Thyroid Carcinoma (FTC) (~10%):
- Histopathology: Composed of uniform follicular cells. Cannot be diagnosed by FNA biopsy (FNA cannot distinguish benign follicular adenoma from carcinoma because diagnosis requires histological demonstration of capsular or vascular invasion).
- Behavior: Spreads hematogenously to bone and lungs.
- Management: Diagnostic lobectomy; if pathology demonstrates capsular/vascular invasion, completion thyroidectomy followed by RAI ablation.
-
Medullary Thyroid Carcinoma (MTC) (~3–5%):
- Pathophysiology: Neuroendocrine tumor derived from calcitonin-secreting parafollicular C-cells (neural crest origin). Amyloid stroma on histology.
- Genetics: 25% are hereditary, caused by germline RET proto-oncogene mutations as part of MEN 2A (MTC, Pheochromocytoma, Primary Hyperparathyroidism) or MEN 2B (MTC, Pheochromocytoma, Mucosal neuromas, Marfanoid habitus).
- Tumor Markers: Serum Calcitonin (correlates with tumor burden) and Carcinoembryonic Antigen (CEA).
- MANDATORY EXAM RULE: Before performing neck surgery on newly diagnosed MTC, always screen for Pheochromocytoma (plasma free metanephrines). If pheochromocytoma is present, resect the pheochromocytoma FIRST to prevent intraoperative hypertensive crisis. MTC does NOT concentrate radioactive iodine.
-
Anaplastic (Undifferentiated) Thyroid Carcinoma (ATC) (~1–2%):
- Behavior: Highly aggressive malignancy in elderly patients presenting with a rapidly enlarging anterior neck mass, severe compressive symptoms (dysphagia, stridor, hoarseness from vocal cord paralysis), and early local/distant invasion. Median survival is 3–6 months.
- Management: Airway protection/palliative tracheostomy, radiation, and targeted therapy (Dabrafenib + Trametinib if BRAF V600E-mutated).
Test Your Knowledge
A 34-year-old woman presents to the clinic with a 2-week history of palpitations, heat intolerance, nervousness, and anterior neck discomfort. She reports having a mild upper respiratory illness 3 weeks ago. On physical examination, her temperature is 37.8°C (100.0°F), blood pressure is 138/82 mmHg, and pulse is 108 bpm. Neck examination reveals an exquisitely tender, mildly enlarged thyroid gland without discrete nodules or bruits. Laboratory testing shows: TSH < 0.01 mIU/L (normal 0.4–4.5), Free T4 2.8 ng/dL (normal 0.8–1.8), and Erythrocyte Sedimentation Rate (ESR) 88 mm/hr (normal < 20). A 24-hour radioactive iodine uptake (RAIU) scan demonstrates a diffuse uptake of 0.8% (normal 15–30%). Which of the following is the most appropriate initial therapy?
A
B
C
D
Test Your Knowledge
A 42-year-old man is evaluated for a firm, painless 1.8-cm solitary thyroid nodule discovered during a routine physical exam. Serum TSH is 1.8 mIU/L (normal 0.4–4.5). Fine-needle aspiration (FNA) biopsy of the nodule demonstrates sheets of cells with amyloid deposits, and immunohistochemistry stains strongly positive for calcitonin. Subsequent germline genetic testing confirms a pathogenic mutation in the RET proto-oncogene. Which of the following is the most essential diagnostic test to perform before referring the patient for total thyroidectomy?
A
B
C
D