Diagnosis is usually suspected when the thyroid suddenly becomes swollen, tender (painful on pressure) and painful especially if associated with hyperthyroidism.

I. Thyroid function test

  • Diagnosis is confirmed by low radioactive iodine uptake(thus distinguishing Subacute thyroiditis from Grave’s disease) and increased T3 and T4.

II. Other blood test

  • ESR (Erythrocyte sedimentation rate) is markedly elevated.
  • Antithyroid antibodies are low (distinguishing Subacute thyroiditis from Hashimoto’s thyroiditis)

III. Fine needle aspiration biopsy shows characteristic giant multinucleated cells in the aspirated material microscopically.