What is the typical presentation of toxic nodular goiter?

Toxic Nodular Goiter Typically Presents with Cardiac Arrhythmias

Toxic nodular goiter most commonly presents with cardiac arrhythmias, particularly atrial fibrillation, due to the effects of excess thyroid hormone on the cardiovascular system. 1

Clinical Presentation of Toxic Nodular Goiter

Toxic nodular goiter (TNG) is characterized by autonomously functioning thyroid nodules that produce excess thyroid hormone, leading to thyrotoxicosis. The clinical presentation differs from other causes of hyperthyroidism like Graves' disease in several important ways:

Common Clinical Features:

• Cardiac manifestations: Most frequent presentation, especially in elderly patients 2

  • Arrhythmias (particularly atrial fibrillation)
  • Tachycardia
  • Palpitations

• Insidious onset: Unlike Graves' disease, symptoms develop gradually 2

  • Often preceded by a long phase of subclinical hyperthyroidism (normal thyroid hormones with suppressed TSH)
  • Many patients may be asymptomatic for years

• Goiter characteristics:

  • Palpable nodular goiter (single or multiple nodules)
  • Usually long-standing
  • Irregular contour on examination

Distinguishing from Other Forms of Hyperthyroidism:

Toxic nodular goiter differs from Graves' disease in several key aspects:

1. Absence of eye signs: Ophthalmopathy (exophthalmos, lid lag, etc.) is characteristic of Graves' disease but not seen in toxic nodular goiter 1, 3

2. No bruit over the gland: While a thyroid bruit may be present in Graves' disease due to increased vascularity, it is not typically found in toxic nodular goiter

3. No dermatological manifestations: Pretibial myxedema and thyroid acropachy are specific to Graves' disease and absent in toxic nodular goiter 1

Diagnostic Approach

The diagnosis of toxic nodular goiter involves:

1. Laboratory tests:

   • Suppressed TSH
   • Elevated free T3 and/or T4
   • Absence of TSH receptor antibodies (which would suggest Graves' disease)

2. Imaging:

   • Thyroid ultrasound: Shows single or multiple nodules with heterogeneous echogenicity 1
   • Radionuclide scan: Reveals hyperfunctioning nodule(s) with suppression of surrounding thyroid tissue 1
     • Iodine-123 is preferred over iodine-131 due to superior imaging quality

Management Considerations

Treatment options for toxic nodular goiter include:

1. Medical therapy: Antithyroid drugs like methimazole can control hyperthyroidism temporarily but rarely lead to permanent remission 4, 2

2. Definitive treatment:

   • Radioactive iodine: Effective for definitive treatment, especially in elderly patients 5, 2
   • Surgery: Indicated for large goiters, compressive symptoms, or when malignancy is suspected 6, 7

Clinical Pearls and Pitfalls

• Cardiac complications: The most serious consequence of untreated toxic nodular goiter is cardiac arrhythmia, particularly atrial fibrillation, which can lead to significant morbidity and mortality 2

• Age considerations: Toxic nodular goiter is more common in older adults, especially in iodine-deficient regions 2

• Treatment response: Unlike Graves' disease, toxic nodular goiter rarely achieves permanent remission with antithyroid drugs alone, necessitating definitive treatment 2

• Subclinical phase: Many patients may have subclinical hyperthyroidism for years before developing overt symptoms, highlighting the importance of thyroid function monitoring in patients with nodular goiter 2