MS ENT University Exam Answers (10 Marks Each)

Q1. Solitary Thyroid Nodule

Definition

Aetiology / Causes of a Solitary Thyroid Nodule

Features Suggesting Malignancy (Red Flags)

• Age <20 or >60 years
• Male sex (higher malignancy risk)
• Rapid increase in size
• Hoarseness (RLN involvement)
• Dysphagia, stridor
• History of head/neck irradiation (especially low-dose external beam - 40% chance of malignancy; radiation risk peaks 20-30 years after exposure)
• Family history of thyroid cancer, MEN2, FAP, Cowden syndrome
• Complaint of pain (may indicate hemorrhage, thyroiditis, or malignancy)

• Hard, irregular, fixed nodule
• Cervical lymphadenopathy
• Vocal cord palsy
• Horner's syndrome
• Dilated veins / Pemberton's sign (retrosternal extension)

Investigations

1. Blood Tests

• Serum TSH - first-line test; if suppressed, suggests a functioning (hot/autonomous) nodule
• Free T3, T4
• Serum calcitonin (if medullary carcinoma suspected)
• TFT for thyroid autoantibodies (anti-TPO, anti-Tg for Hashimoto's)

2. Ultrasonography (USG Neck)

• Investigation of choice for initial evaluation
• Determines: solid vs cystic, size, echogenicity, calcification, margins, vascularity (Doppler)
• Features suspicious of malignancy: hypoechoic, microcalcifications (psammoma bodies), irregular margins, taller-than-wide shape, central vascularity

3. FNAC (Fine Needle Aspiration Cytology)

• The single most important and cost-effective investigation
• Performed under USG guidance for non-palpable or complex nodules
• Bethesda system classification (I-VI):
  • I: Non-diagnostic
  • II: Benign
  • III: Atypia of undetermined significance (AUS)
  • IV: Follicular neoplasm
  • V: Suspicious for malignancy
  • VI: Malignant

4. Thyroid Scan (Radionuclide Scintigraphy)

• Uses 99mTc pertechnetate (obtained at 30 min) or 131I (at 24 hours)
• Hot nodule = hyperfunctioning; rarely malignant (<1%)
• Cold nodule = non-functioning; 10-20% risk of malignancy
• A single non-functioning (cold) thyroid nodule is an indication for surgery
• Useful when: solitary nodule palpated, suspected retrosternal goitre, ectopic thyroid

5. CT/MRI Neck and Chest

• For retrosternal extension, tracheal compression, mediastinal nodes
• CT with contrast avoided if RAI therapy planned (iodine load)

6. Indirect Laryngoscopy

• Mandatory pre-operatively to assess vocal cord mobility

Management

Algorithm:

Solitary Nodule
     ↓
TSH + USG
     ↓
FNAC (USG-guided)
     ↓
Bethesda I → Repeat FNAC
Bethesda II → Follow-up USG every 1-2 years
Bethesda III/IV → Repeat FNAC or hemithyroidectomy
Bethesda V/VI → Surgery

Surgical Options:

• Hemithyroidectomy (lobectomy + isthmusectomy) - for benign or indeterminate lesions
• Total thyroidectomy - for confirmed malignancy, bilateral disease, history of radiation, large nodules >4 cm
• Followed by radioiodine ablation (for differentiated thyroid cancer) + TSH suppression therapy

Non-surgical:

• TSH suppression with thyroxine (limited role; used in select cases)
• USG follow-up for Bethesda II nodules
• Ethanol ablation or thermal ablation for benign symptomatic cysts

Q2. Thyrotoxicosis

Definition

Classification / Types

Pathophysiology

• Graves': TSH-receptor antibodies (TSH-RAb) bind to TSH receptors, producing disproportionate and prolonged stimulation of the whole thyroid → diffuse hyperplasia
• Toxic adenoma: Autonomous nodule secretes excess hormones → suppresses TSH → surrounding normal tissue becomes inactive
• Toxic nodular goitre: Internodular tissue becomes overactive (secondary toxicity) OR one/more nodules gain autonomy

Clinical Features

Symptoms:

• Nervousness, anxiety, emotional lability
• Heat intolerance, excessive sweating
• Palpitations (tachycardia, AF)
• Weight loss despite increased appetite
• Diarrhoea / increased bowel frequency
• Oligomenorrhoea / amenorrhoea
• Fatigue, muscle weakness (proximal myopathy)
• Tremor of hands
• Hair loss (diffuse alopecia)
• Insomnia

Signs:

Histology of thyrotoxicosis:

• Hyperplasia of acini lined by high columnar epithelium
• Many acini are empty; others contain vacuolated colloid with a characteristic "scalloped" pattern adjacent to the thyrocytes

Investigations

1. Serum TSH - decreased (suppressed) in primary thyrotoxicosis; increased in secondary (TSH-secreting pituitary adenoma)
2. Free T3 and Free T4 - elevated
3. TSH-receptor antibodies (TSH-RAb/TSI) - positive in Graves' disease
4. Radioiodine uptake scan - diffusely increased in Graves'; hot nodule(s) in toxic adenoma; patchy in MNG
5. T3 suppression test (Werner test) - differentiates thyrotoxicosis from other causes; only ~10-20% suppression in thyrotoxicosis (normal >50%)
6. CBC, LFTs, ECG - baseline before antithyroid drugs; AF on ECG
7. Serum calcium, PTH - pre-op
8. Indirect laryngoscopy - mandatory pre-op

Treatment

Three pillars: Antithyroid drugs | Surgery | Radioiodine

1. Antithyroid Drugs

• Carbimazole (drug of choice) and propylthiouracil (PTU)
• Mechanism: Inhibit thyroid peroxidase - block T3/T4 synthesis; PTU also inhibits peripheral T4→T3 conversion
• Carbimazole 30-40 mg/day; reduce to maintenance (5 mg 8-hourly) once euthyroid (8-12 weeks); or use block-and-replace regimen
• Duration: 6 months (mild) to 2 years (severe)
• Failure rate: at least 55% (cannot cure toxic nodule; antithyroid drugs cannot stop autonomous tissue)
• Advantages: No surgery, no radiation
• Side effects: Agranulocytosis (0.3%), rash, hepatotoxicity (PTU)

• Control adrenergic symptoms: palpitations, tremor, sweating
• Propranolol also inhibits peripheral T4→T3 conversion
• Response is rapid (days vs weeks with carbimazole)
• Must continue for 7 days post-operatively (hormone levels remain high)

2. Surgery (Thyroidectomy)

• Render the patient euthyroid with carbimazole (8-12 weeks) OR rapid preparation with propranolol
• Potassium iodide / Lugol's iodine for 10 days pre-op (reduces vascularity of gland, reduces intraoperative bleeding)
• Block-and-replace: High-dose carbimazole + thyroxine 0.1-0.15 mg/day; last dose of carbimazole the evening before surgery

• Diffuse toxic goitre / Toxic MNG with overactive internodular tissue → Subtotal thyroidectomy (reduces thyroid below critical mass) OR Total/near-total thyroidectomy (eliminates recurrence risk, simplifies follow-up; requires lifelong thyroxine)
• Toxic adenoma / Autonomous toxic nodule → Excision of nodule OR lobectomy (removes all overactive tissue; allows suppressed normal tissue to recover)
• Toxic nodular goitre (large/uncomfortable) → Surgery preferred (less responsive to RAI; enlarges further with antithyroid drugs)

• RLN injury (unilateral hoarseness; bilateral = stridor/airway emergency)
• Hypoparathyroidism (hypocalcaemia, tetany)
• Thyroid storm (if inadequately prepared)
• Haemorrhage (wound haematoma - life-threatening if compresses airway)
• Hypothyroidism (especially after total thyroidectomy)

3. Radioiodine (131I)

• Destroys thyroid cells; reduces functioning tissue below critical mass
• Indication: Diffuse toxic goitre (first-line for relapse after antithyroid drugs); toxic adenoma in patients >45 years (suppressed normal tissue does not take up iodine - minimal risk of delayed insufficiency)
• Contraindications: Pregnancy, breastfeeding, children (use short half-life isotopes only), progressive eye signs (can aggravate)
• Advantages: No surgery, no prolonged drug therapy
• Disadvantages: Isotope facilities required; patient quarantine; avoid close contact with children; pregnancy deferred; may worsen exophthalmos

Choice of Treatment Summary

Thyroid Storm (Complication of Untreated Thyrotoxicosis)

• Acute, life-threatening hypermetabolic state
• Precipitated by: Infection, surgery, trauma, withdrawal of ATDs, radioiodine, labour and delivery, DKA
• Features: High fever, tachycardia/AF, CNS agitation/seizures, GI: vomiting/jaundice, cardiovascular failure
• Mortality: 8-25%
• Treatment: IV propranolol, IV PTU/carbimazole, Lugol's iodine (1 hour after ATDs), hydrocortisone, cooling, IV fluids, treat precipitant