Thyroid and Parathyroid Surgery

Autoimmune and autonomous (hyperfunction) mechanisms

• Graves' disease: TSI-driven receptor stimulation; surgery is chosen when antithyroid drugs fail or cause agranulocytosis/hepatotoxicity, when the goiter is large or compressive, or when moderate-to-severe orbitopathy makes radioiodine undesirable (American Thyroid Association hyperthyroidism guideline).
• Toxic adenoma / toxic multinodular goiter: somatic activating TSHR or GNAS mutations create TSH-independent nodules; long-standing iodine deficiency predisposes, and an iodine load (contrast, amiodarone) can unmask thyrotoxicosis (Jod-Basedow).

Neoplastic mechanisms

• Papillary carcinoma: BRAF V600E and RET/PTC rearrangements; the histology most tightly linked to prior ionizing radiation.
• Follicular carcinoma: RAS and PAX8-PPARγ; hematogenous spread to bone and lung.
• Medullary carcinoma: parafollicular C cells; germline RET in MEN2A/2B and familial MTC — prophylactic thyroidectomy is indicated in gene carriers (ATA medullary thyroid carcinoma guideline).
• Anaplastic carcinoma: dedifferentiation with TP53 loss in an elderly patient with a long-standing goiter.

Parathyroid mechanisms

• Sporadic single adenoma: clonal, with cyclin D1 (PRAD1) rearrangement or MEN1 loss.
• Four-gland hyperplasia: germline MEN1 or RET (MEN2A) — think multiglandular disease in a young patient.
• Parathyroid carcinoma: CDC73/HRPT2 loss; very high calcium plus a palpable neck mass.
• Secondary/tertiary hyperparathyroidism: CKD-driven phosphate retention and calcitriol deficiency, with eventual autonomous glands (KDIGO CKD-MBD framework).

Thyroid Pathology Leading to Surgery

• Graves' disease: Thyroid-stimulating immunoglobulin (TSI) binds TSH receptors, causing persistent thyroid hyperplasia and hormone overproduction refractory to medical/radioactive iodine therapy
• Thyroid cancer (papillary, follicular, medullary, anaplastic): Malignant transformation of thyroid follicular or C cells; papillary is most common (~80%) with better prognosis; anaplastic is most aggressive
• Toxic multinodular goiter: Multiple autonomous nodules producing excess thyroid hormone independent of TSH suppression
• Compressive goiter: Benign thyroid enlargement causing airway obstruction, dysphagia, or superior vena cava syndrome

Parathyroid Pathology Leading to Surgery

• Primary hyperparathyroidism: Autonomous PTH production from adenoma (80%), hyperplasia (15-20%), or carcinoma (<5%); causes hypercalcemia through increased bone resorption, renal tubular reabsorption of calcium, and 1,25-dihydroxyvitamin D production
• Secondary hyperparathyroidism: Chronic kidney disease causes phosphate retention and PTH elevation; surgical intervention reserved for refractory cases

Hyperthyroidism (Graves' disease)

• Thyroid-specific: Diffuse goiter, lid lag, lid retraction, exophthalmos (eye protrusion from orbital inflammation), pretibial myxedema
• Constitutional: Palpitations, tachycardia at rest, heat intolerance, tremor, anxiety, insomnia, weight loss despite increased appetite
• Thyroid storm (surgical emergency): Fever, severe tachycardia, altered mental status, cardiovascular collapse

Thyroid Cancer Presentation

• Often asymptomatic; discovered incidentally on imaging or during workup for other symptoms
• Palpable thyroid nodule or neck mass; papillary cancer may present with cervical lymph node involvement
• Hoarseness (recurrent laryngeal nerve involvement), dysphagia, neck/throat pain indicate advanced disease

Primary Hyperparathyroidism

• Symptomatic: Nephrolithiasis ("stones"), osteoporosis/pathologic fractures ("bones"), hyperactive bowel/peptic ulcer disease ("groans"), psychiatric symptoms ("psychiatric overtones")
• Often asymptomatic; discovered on routine lab work showing hypercalcemia
• Severe hypercalcemia (>13 mg/dL): Confusion, lethargy, muscle weakness, nausea/vomiting, polyuria, polydipsia

Parathyroid Hyperplasia

• Often associated with MEN syndromes (MEN1 or MEN2A); presents earlier and more severely than adenoma
• Multiglandular involvement causing more profound hypercalcemia

Thyroid Disorders

• TSH and free T4: TSH suppressed, elevated free T4 in Graves' disease; TSI antibodies confirm Graves' (not required if clinical diagnosis clear)
• Thyroid ultrasound: Characterizes nodules (size, echogenicity, vascularity); guides FNA biopsy
• Fine Needle Aspiration (FNA) with Bethesda Classification: Gold standard for nodule cytology; results stratify malignancy risk and guide management
• TSH suppression test: For suspicious nodules; lack of suppression suggests autonomous function
• 131I uptake scan: Elevated diffuse uptake in Graves'; absent uptake suggests thyroiditis or factitious hyperthyroidism

Parathyroid Disorders

• Serum calcium (ionized preferred), phosphate, PTH: Elevated PTH with hypercalcemia confirms hyperparathyroidism; PTH-independent causes (malignancy, vitamin D intoxication) show suppressed PTH
• 24-hour urine calcium: High levels increase surgical urgency; low urine calcium suggests familial hypocalciuric hypercalcemia (FHH—genetic disorder mimicking hyperparathyroidism, no surgery indicated)
• Serum creatinine/eGFR: Assess kidney function; guides operative decision-making
• Parathyroid imaging (Sestamibi scan, ultrasound, CT): Localizes abnormal glands; Sestamibi scan has ~90% sensitivity for adenomas
• Intraoperative PTH monitoring: >50% drop from baseline predicts successful adenoma removal

Important diagnostic considerations

• FHH presents with hypercalcemia, hypercalciuria, and elevated PTH but has normal/low urine calcium-to-creatinine ratio; surgery contraindicated
• Asymptomatic hyperparathyroidism: 2015 guidelines recommend surgery if age <50, serum calcium >1 mg/dL above upper normal, creatinine clearance <60 mL/min, or T-score <-2.5 on bone density scan

Thyroid Surgery (Thyroidectomy)

• Graves' disease: Patient preference over antithyroid drugs/radioactive iodine; large goiter; complications of medical therapy; pregnancy
• Thyroid cancer: Nearly all cases require thyroidectomy; extent depends on histology and stage
• Symptomatic goiter: Airway compression, dysphagia, cosmetic concerns unresponsive to medical therapy

• Achieve euthyroid state with antithyroid drugs (PTU or methimazole); PTU preferred in first trimester pregnancy
• Lugol's iodine (potassium iodide solution) 7-10 days preoperatively: Reduces gland vascularity and blocks hormone release
• Beta-blockers: Manage adrenergic symptoms; non-selective agents preferred (propranolol) as they inhibit peripheral T4→T3 conversion
• Thyroid storm prophylaxis: Critical in Graves' disease; inadequate preparation risks intraoperative crisis

• Subtotal thyroidectomy: Leaves 5-10g of thyroid tissue (mostly posterior) to preserve function; reduces hypothyroidism risk but increases recurrence risk in malignancy
• Total thyroidectomy: Complete removal of all thyroid tissue; indicated for cancer, provides surveillance via TSH suppression and radioactive iodine therapy
• Bilateral vs. unilateral: Bilateral for malignancy/Graves'/hyperplasia; unilateral for solitary nodules with preoperative assessment of contralateral side

• Hypothyroidism is universal after total thyroidectomy; initiate levothyroxine ~1.6 mcg/kg/day, titrate to TSH goal
• For cancer: Maintain TSH suppression (TSH <0.5 mIU/L) depending on risk stratification
• Reassess thyroid function 6-8 weeks after surgery, then annually

Parathyroid Surgery (Parathyroidectomy)

• Symptomatic hyperparathyroidism: Definitive indication; surgery cures ~95% of cases
• Asymptomatic cases if any of: serum calcium >1 mg/dL above normal, age <50, creatinine clearance <60 mL/min, T-score ≤-2.5, or 24-hour urine calcium >400 mg/day

• Bilateral neck exploration (traditional): Four-gland inspection; identifies adenoma vs. hyperplasia;

Airway emergencies — recognize immediately

• Expanding cervical hematoma: venous or arterial bleeding in a closed compartment causes venous congestion and supraglottic edema, not tracheal compression alone. Signs are a tense swollen neck, drain output, and stridor. Treatment is to open the incision and evacuate the clot at the bedside, then go to the OR — do not wait for imaging.
• Bilateral recurrent laryngeal nerve injury: both cords sit paramedian, producing biphasic stridor and respiratory distress on extubation with a near-normal voice. Requires immediate reintubation, and tracheostomy if the injury does not resolve.
• Thyroid storm: fever, delirium, and high-output failure in an inadequately prepared Graves' patient; managed with beta blockade, thionamide before iodine, and glucocorticoids.
• Hypocalcemic tetany with laryngospasm or seizure: treat with IV calcium gluconate and correct magnesium.

Nerve injury

• Unilateral RLN injury: hoarse, breathy voice with aspiration on thin liquids; the nerve lies in the tracheoesophageal groove near the inferior thyroid artery. The AAO-HNS voice-outcomes guideline supports documenting voice and obtaining laryngoscopy when the voice is abnormal or the case is reoperative.
• External branch of the superior laryngeal nerve: loss of cricothyroid tension — the opera singer's nerve — causing voice fatigue and inability to reach high pitch; injured with high ligation of the superior thyroid artery.

Calcium and endocrine sequelae

• Hypoparathyroidism: devascularized or resected glands; perioral paresthesias, Chvostek and Trousseau signs, prolonged QT, low calcium with high phosphate and low PTH, typically at 24–72 hours.
• Hungry bone syndrome: post-parathyroidectomy remineralization in severe disease with high alkaline phosphatase; low calcium with low phosphate and low magnesium — the discriminator from hypoparathyroidism.
• Hypothyroidism: universal after total thyroidectomy.
• Persistent/recurrent hyperparathyroidism: missed ectopic gland (thymus, mediastinum, carotid sheath, intrathyroidal) or supernumerary gland.

• Stridor after thyroidectomy has two answers: a tense, swelling neck means hematoma — open the incision at the bedside; a soft neck with a near-normal voice and biphasic stridor means bilateral RLN palsy — reintubate. Choosing "CT of the neck" for a compromised airway is the trap.
• Nonrecurrent laryngeal nerve is right-sided: it accompanies an aberrant right subclavian artery (arteria lusoria) and is at high risk because the surgeon expects the nerve in the tracheoesophageal groove.
• Phosphate separates the two post-op hypocalcemias: high phosphate = hypoparathyroidism; low phosphate with low magnesium and a preoperatively high alkaline phosphatase = hungry bone syndrome.
• In MEN2A, resect the pheochromocytoma first: unopposed catecholamine release during thyroidectomy can precipitate hypertensive crisis. Screening for pheochromocytoma and hyperparathyroidism before medullary thyroid carcinoma surgery is an ATA recommendation, and "proceed to total thyroidectomy now" is the standard distractor.
• FNA cannot diagnose follicular carcinoma: capsular or vascular invasion is required, so a Bethesda follicular neoplasm result leads to diagnostic lobectomy, not repeat FNA. Papillary carcinoma, by contrast, is an FNA diagnosis — Orphan Annie eye nuclei, nuclear grooves, and psammoma bodies, spreading via lymphatics.
• Familial hypocalciuric hypercalcemia is the classic "don't operate" stem: inactivating CASR mutation, lifelong mild hypercalcemia, normal-to-mildly-high PTH, family history, and a urinary calcium-to-creatinine clearance ratio below about 0.01. Parathyroidectomy does not correct it.
• Prepare Graves' patients in order: thionamide to euthyroid, beta blockade (propranolol also blunts T4→T3 conversion), then Lugol's iodine in the final week. Giving iodine before a thionamide can fuel hormone synthesis.
• Intraoperative PTH has a short half-life (minutes), which is why a greater than 50% fall from baseline after excision predicts cure; failure to fall means a second hyperfunctioning gland — convert to bilateral exploration (AAES guideline).