Thyroid Nodule

Intro & Epidemiology

• 4-7% of population have palpable thyroid nodules, 19-67% have incidental nodules on ultrasound
• 5% of palpable nodules are malignant (<1% of nodules cause hypothyroidism or thyrotoxicosis)
• Nodules <1cm are not usually palpable (unless anterior)
• Majority are benign, the key goal is to rule out cancer.
• Pain is uncommon (if painful likely benign)

Review of Thyroid Symptoms

• Hyperthyroidism:
  • wt loss (good appetite), anxiety, intolerance toheat, sweating, hair loss, muscle pains, weakness, tremor, irritibility/hyperactivity.
  • nervousness, irritability, increased perspiration, palpitations, hand tremors, anxiety, poor sleep, thinning skin, brittle hair, muscle weakness, frequent BM, wt loss, good appetite, menstruation may lighten.
• Hypothyroidism
  • Early (cold intolerance, constipation, wt gain, bradycardia, sweating, muscle/joint pains, dry/itchy skin, thin/brittle fingernails, depression, infertility (cycles irregular), elevated lipids, hyperprolactinemia, galactorrhea.

Risk Factors ("Red Flags")

• Extremes of age (<20yo or >65yo)
• Male Gender
• Symptoms of local invasion ("dysphagia, neck pain, hoarseness)
• History of neck radiation
• Family history of thyroid cancer or polyposis (Gardner's Syndrome)

Physical Exam:

• Thyroid exam
• Lymph nodes

Differential Diagnosis

• Solitary:
  • Cyst
  • Thyroid Adenoma (Benign Tumour - "Hot" or "Cold")
  • Thyroid Carcinoma
    • Papillary
    • Follicular
    • Medullary
    • Anaplastic
  • Lymphoma
  • Thyroglossal Duct Cyst
  • Reidel's Struma
• Multiple - Multinodular Goiter

Classification

Diagnostic Algorithm

• 1st Thing: Is TSH suppressed?

  • If Low --> Thyroid Scan and Radioactive Iodine Uptake

    If Not Low --> Thyroid Ultrasound +/- FNA

    • If FNA = Benign --> continue regular F/U
    • If FNA = Insufficient --> Repeat FNA (US guidance)
    • If FNA = Follicular neoplasm or malignant --> Call Surgeon

     

• Thyroid Antibody Levels appropriate in pts with multinodular goitres or autoimmune suspected
• Calcitonin Measurement NOT recommended (fused to follow disease activity in medullary thyroid cancer)
  • Used to follow disease activity in medullar thyroid cancer.
  • MEN2 or related disorders.
• Serum Thyroglobulin level 
  • Primary tumor marker with well differentiated thyroid cancer who had thyroidectomy and RAI Ablation.

Based on the American Association of Clinical Endocrinologists (taken from AAFP website)

Diagnostic Tests

• Ultrasound

  • ALL patients with new thyroid nodules should undergo U/S to assess:
    • Confirm the presence
    • Malignant Features
      • Hypoechoic
      • Hypervascular
      • Microcalcifications
      • Irregular Border 
      • Taller than Wide on saggital view
      • Size > 3cm
    • Benign Features:
      • Comet Tail
      • Increased peripheral nodule vascularity
      • Hyperechoic
      • Halo present
      • Pure Cyst
    • Presence of additional nodules
    • Lymphadenopathy.
• CT/MRI not indicated, unless suspect substernal goitre or cervical adenopathy or tracheal compression.

• Radioactive Iodine Uptake Scan (RAI scan)

  • Useful if euthyroid, but multiple nodules - to see which nodules are concerning
  • Useful if thyrotoxic (low TSH), to see if nodule is cold (risk of cancer) or hot (no risk of cancer)

• TSH

  • Based on several studies, correlates with risk of cancer and severity.
    • If TSH is low, indicating overt or subclinical hyperthyroidism, the possibility of hyperfunctioning nodule is increased and should do RAI scan.
    • If TSH is normal or elevated, meets criteria for sampling, need FNA bx. + evaluate for hypothyroidism.
  • Based on one study (J Clin Endocrinol Metab. 2006;91(11):4295.)
    • 2.8, 3.7, 8.3, 12.3, and 29.7 percent for patients with serum TSH concentrations <0.4 mU/L, 0.4 to 0.9 mU/L, 1.0 to 1.7 mU/L, 1.8 to 5.5 mU/L, and >5.5

    • TSH	Risk of Thyroid Ca
      <0.4 mU/L	2.8%
      0.4 mU/L	3.7%
      0.9 mU/L	8.3%
      1.0 mU/L	12.3%
      1.7 mU/L	29.7%

• FNA Biopsy
  • Any solid & hypoechoic nodules >1cm should be biopsied
    • Or >2cm if mixed (cystic and solid)    
  • No biopsy necessary if:   (Consider if significant risk factors!)
    • Smaller than 1cm
    • Not growing on annual U/S exam
    • Pure Cyst
    • Hot Nodule

Treatment

• Call Surgery if:
  • Malignant Nodules
  • Hypoparathyroidism
  • Recurrent Laryngeal nerve paresis
  • >4cm & ass'd worrisome findings (cervical lymphadenopathy, hoarseness, external radiation, lab findings).
• Benign Nodules
  • Monitor with periodic neck exams & ultrasound (q6-18mo)
  • Repeat FNA biopsy recommended if grown in interval (>50% by volume, or >20% in 2-dimensions, or suspicious findings)
  • If stable >18mo, can change screening for q3-5y
•  

Multinodular Goiter

• In iodine-sufficient areas, has both solid and partially cystic thyroid nodules.
• More common in older patients.
• Over time can grow to require treatment.
• Dx:
  • FNA needed to exclude cancer
• Complications:
  • Can impinge on esophagus and recurrent laryngeal nerve
    • --> dyspnea, stridor, cough, fullness sensation, hoarseness.
  • Some nodules can become large enough to suppress TSH and make pt thyrotoxic.
• Tx:
  • Thyroidectomy if causes compressive symptoms or thyrotoxic.
  • Use methimazole for thyrotoxic pts.
  • Radio-iodine 131I -> decreases size, but not first line.  (useful if thyrotoxic, doesn't reliably shrink the gland).