toxic multinodular goiter (Plummer's disease)

Etiology

• iodinated contrast administration & other sources of iodine can precipitate hyperthyroidism in patients with underlying thyroid disease

Epidemiology

• most common cause of hyperthyroidism in the elderly
• it occurs in <1/2 of patients with multinodular goiter

Clinical manifestations

• thyroid nodules & thyroid asymmetry
• cardiovascular manifestations tend to predominate
• differs from Grave's disease clinically:
  • no associated ophthalmopathy
  • no associated dermopathy
  • hypermetabolism is less severe

Radiology

• thyroid scintigraphy with radioactive iodine uptake 3-4 weeks after exposure to contrast to evaluate for functioning nodules
• patchy uptake in an enlarged gland with apparent hyperfunction
  • the one lobe may show uniform uptake, the other pathchy uptake

Differential diagnosis

• subacute thyroiditis
  • thyrotoxicosis after an upper respiratory viral infection or postviral inflammatory process.
  • neck pain or tenderness, elevated serum C-reactive protein
• Graves disase
  • positive thyrotropin receptor antibodies
  • associated ophthalmopathy, dermopathy
• TSH-secreting pituitary adenoma
  • elevated free T4 & serum total T3
  • elevated or inappropriately normal serum TSH

Management

• beta-blockers:
  • decrease beta-adrenergic mediated effects of thyrotoxicosis
  • decrease peripheral conversion of T4 to T3
  • indicated for all forms of thyrotoxicosis
  • titrate according to heart rate
  • propranolol 20-40 mg PO QID
• radioactive I-131 ablation
• subtotal thyroidectomy may be treatment of choice
  • near-total or total thyroidectomy if bilateral hyperfunctioning nodules
• methimazole for subclinical hypothyroidism in the elderly

More general terms

• multinodular goiter

Additional terms

• hot nodule; toxic thyroid adenoma
• hyperthyroidism