23rd May 2025

Thyroiditis

Thyroiditis refers to a transient state of thyrotoxicosis followed by hypothyroidism features. It occurs due to gland inflammation. It is more common in women, with a peak incidence of 30-50 years old. 

Causes of thyroiditis include: 

• Hashimoto’s disease (discussed later on in this chapter)
• Post-partum thyroiditis
  • Usually occurs within 6 months of giving birth. 
  • It occurs in about 30-52% of patients of +ve TPO antibodies. 
  • Is associated with type 1 diabetes 
  • Most patients show complete remission with fewer incidence of permanent hypothyroidism as a complication.

• Drug-induced e.g., amiodarone, lithium, interleukin 2 or interferon-α(due to thyroid peroxidase antibodies formation in 15% of the cases).
• Subacute (De Quervain’s thyroiditis)
  • May occur due to granuloma formation, usually associated with viral upper respiratory tract infection (mumps, coxsackie, influenza, adenovirus, and echovirus). 
  • May also occur due to lymphocytic infiltration, which may occur in the post-partum period, in association with autoimmune disease, or as a side effect of a drug. 
  • Has a triphasic picture: 
    • The thyrotoxic phase occurs due to the inflammatory damage of the follicular cells, releasing thyroid hormones (pre-formed colloid). 
    • The hypothyroid phase follows due to the depletion of the thyroid hormones and reduced synthesis as a result of follicular cell damage. 
    • The euthyroid phase is achieved where, a recovery of the thyroid gland occurs with pathological changes and the thyroid function normalises

• Riedel’s thyroiditis
  • A rare condition characterised by extensive thyroid gland fibrosis and the surrounding structure. 
  • One third of the patients have associated extracervical manifestations for example: pulmonary, sclerosing cholangitis, mediastinal, and retroperitoneal fibrosis. Parathyroid glands fibrosis is rare. 
  • Patients are usually in euthyroid state. 30% of the patients develop hypothyroidism eventually with extensive fibrosis. 
  • Malignancy should be excluded.
• Radiation
• Pyogenic 
  • e.g., Staphylococcus aureus, streptococci, Escherichia coli, tuberculosis, fungal. 
  • Usually caused by another septic focus. 
  • Piriform sinus infection should be excluded.

Clinical picture

The clinical picture depends on the cause of thyroiditis: 

• Patients may present with features consistent with hypothyroidism or hyperthyroidism
• In suppurative and subacute causes, painful tender glands and fever is common. 
• With subacute thyroiditis, there is usually a prior history of upper respiratory tract infection, generalised malaise, and arthralgia. 
• Hashimoto’s disease, as will be described later, is usually associated with goitrous appearance and a clinical picture of hypothyroidism. 
• With Riedel’s thyroiditis, a hard woody consistency of the thyroid may be noted. Patients are usually euthyroid in Riedel’s thyroiditis.

Investigations

• Erythrocyte sedimentation rate (ESR) or  C-reactive protein (CRP) are raised in a state of inflammation.
• TFTs will show either a picture of hyper or hypothyroidism depending on the cause of the thyroiditis.
• Anti-TPO might be elevated.
• Thyroid scintigraphy 
  • Radionuclide uptake is reduced in subacute thyroiditis (due to follicular cell damage).
  • Inconclusive in acute and chronic conditions.
• Thyroid US 
  • Some nodular pattern and cobblestone appearance are seen in subacute thyroiditis (due to reduced vascularity and hypoechoic regions)
• FNAC 
  • Can show lymphocytic or granulomatous picture in subacute thyroiditis. Aspiration culture should be sent in acute cases.

Management

• When it comes to treatment of thyroiditis, two aspects are considered: generic management of symptoms and acute thyroid function change; and management of the underlying cause of the thyroiditis. Patients should have their thyroid function monitored regularly, with the frequency of this depending on the underlying cause.
• In terms of general management, as was discussed previously, the management of hyperthyroidism entails treatment of the hyperactivity as well as treating thyrotoxic symptoms. If hypothyroidism is prevalent, T4 replacement is required.

Management of the different causes of the thyroiditis is summarised in Table 4.

Table 4: Thyroiditis management