Silent thyroiditis

• subacute lymphocytic thyroiditis may present with painless goitrous enlargement or hyperthyroidism, or both. Generally, the levels of T3 and T4 are raised, while thyroid uptake of radioactive iodine is low
  
  
• the condition is relatively common in the USA where it may account for 15% of all cases of hyperthyroidism. It is less common in the UK. Silent thyroiditis may occur at any age but is most frequently reported in the 12 months following childbirth - so called post-partum thyroiditis (1)
  
  
• aetiology is obscure. There is no clear association with viral infection, de Quervains thyroiditis, Hashimoto's disease or primary hypothyroidism. This condition is mediated by antithyroid peroxidase antibodies (formerly known as antimicrosomal antibodies) and thyroid stimulating immunoglobulin (as seen in Graves' disease) are not present (1)
  • comparing Hashimoto's thyrodititis and lymphocytic thyroiditis
    • study evidence suggests (2) apoptosis represents one of significant mechanisms in the pathogenesis of both Hashimoto's thyrodititis and lymphocytic thyroiditis and that lymphocytic thyroiditis probably differs from Hashimoto's thyrodititis
      
      
• morphologically, it is characterised by foci of lymphocytic infiltration, sometimes with increased interstitial fibrous tissue. There are no lymphoid germinal centres and few, if any, plasma cells
  
  
• the condition is self-limiting. Hyperthyroidism is commonly followed by a phase of hypothyroidism may become permanent in 25% of patients (1)
  
  
• patients with this condition are referred for specialist management
  
  
• antithyroid drugs and radioiodine are unhelpful - this is because hyperthyroidism is secondary to thyroid distruction causing increased thyroxine release. Beta blockers may provide symptomatic relief

Reference:

• 1) Lancet 2001; 357 (9270): 1793-6.
• 2)Todorovic J et al. Is lymphocytic thyroiditis a unique type or merely a type of Hashimoto's thyroiditis? Minerva Med. 2014 May 27.
• 3) Franklyn Hypothyroidism. Med. Int. 1993;21:5.