Criteria

Phases of subacute thyroiditis[2][4] JTA: guideline for the diagnosis of subacute thyroiditis (acute phase) Opens in new window

Thyrotoxic phase (up to 3 months)

  • Acute viral-like illness with thyroid (neck) pain, fever, myalgias, malaise, and pharyngitis, which precedes severe neck pain

  • Thyroid destructive phase, with decreased serum thyroid-stimulating hormone (TSH) and raised serum T4 and T3 levels

  • Radioiodine thyroidal uptake with I-123 or Tc-99m low (<1% at 24 hours)

  • Serum ESR and/or CRP levels are usually raised

Hypothyroid phase (up to 6 months, but usually 2-3 months)

  • Serum thyroid hormone levels are usually mildly or moderately low

  • Serum thyroid autoantibody levels may be variably positive

  • Radioiodine thyroidal uptake is not recommended during the hypothyroid phase

Euthyroid phase

  • Serum thyroid function returns to normal in ≥90% of patients; thyroid histology returns to normal in these patients

  • A minority of patients remain permanently hypothyroid and will require indefinite thyroid hormone replacement therapy

Minimal criteria that confirm diagnosis[1][39][40][41]

  • Some disturbance of thyroid function:

    • Low TSH

    • Raised total T4, total T3, free T4 index, free T4, and/or free T3

    • Total T3:total T4 ratio <15

    • Free T3:free T4 <3

  • Clinical signs and symptoms of neck pain, with or without preceding viral illness.

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