Thyroiditis (Subacute/Transient) or De Quervain’s thyroiditis

Background/Epidemiology

• Self-limiting condition which characteristically has three clinical phases
  1. Hyperthyroidism
  2. Hypothyroidism
  3. Euthyroidism
• May be a cause of up to 15% of patients with thyrotoxicosis and up to 10% of patients with hypothyroidism.
• There are also three different pathological types of subacute thyroiditis
  • Subacute granulomatous thyroiditis (de Quervain’s or subacute painful)
  • Subacute Lymphocytic thyroiditis (painless)
  • Subacute post-partum thyroiditis
• As with other thyroid conditions, women are more at risk than men (3-5:1).  Average age of onset is 30-50 years old.

Aetiology/Risk factors

• Subacute granulomatous
  • Most commonly follows an episode of viral illness
  • There are genetic factors that may predispose e.g. HLA-B35
• Lymphocytic
  • Thought to be, at least in part, an autoimmune process, as antibodies (in particular antimicrosomal antibodies and antithyroid peroxidase antibodies) are often present in these patients
  • Can also occur in patients receiving or having received amiodarone or interferon-α treatment. (can present >2 years later)
• Post-partum
  • Also thought to be autoimmune in nature
  • Much rarer in countries with iodine-rich diets
• Other causes include radiotherapy and infective thyroiditis (rare- only really ever seen in immunodeficient patients)

Pathophysiology

• The inflammatory process occurs.  This causes swelling/enlargement of the thyroid gland.  As the process continues, the thyroid follicles are broken down and thyroid hormone is inadvertently released.
• Hyperthyroid phase occurs at this stage.  As the amount of T3/T4 is depleted, patient typically then become euthyroid and then hypothyroid, before recovering to a euthyroid state.
• Histologically, there is a mixture of acute, subacute and chronic granulomatous, inflammatory change associated with follicle destruction.

Presentation

• Typically, patients present with a prodromal illness or infection
  • May complain of flu-like symptoms e.g. fever, malaise, myalgia, sore-throat, anorexia, fatigue etc
  • May have been diagnosed with infection e.g. pharyngitis, measles, mumps etc
  • NB constitutional symptoms may continue with the thyroiditis (even if symptoms of specific infection had resolved)
• Often the thyroid enlarges (often firm enlargement and diffuse)
  • In painful (granulomatous) thyroiditis, the thyroid is usually acutely painful/tender (gradual/sudden)
    • this can start on one site and spread or begin bilaterally
  • Other local symptoms that can occur include
    • dysphagia
    • hoarseness
• NB in post-partum thyroiditis, there is firm, painless enlargement of the thyroid which can occur up to 6 months after birth
• Symptoms of hyperthyroidism and/or hypothyroidism

Investigations

• FBC
  • WCC may or may not be raised.  CRP can be slightly elevated
• Thyroid function tests
  • NB cf toxic nodular disease, if there is hyperthyroidism- fT4 is usually disproportionately elevated compared to fT3
• Radioiodine scan (decreased uptake can distinguish thyroiditis from Grave’s disease – which may otherwise be indistinguishable from painless thyroiditis)

Management

• Because thyroiditis is often self-limiting, no treatment is routinely required (important to diagnose correctly over Graves regarding unnecessary treatment)
• If the patient remains chronically hypothyroid after the episode, replacement thyroxine can be considered.
• If acute hyperthyroid symptoms are really troublesome, beta-blockers can be used for symptomatic relief