Which laboratory tests are essential for diagnosing autoimmune thyroiditis in primary care?

For diagnosing autoimmune thyroiditis in primary care, the essential laboratory tests typically involve assessing thyroid function and specific antibodies:

• Initial Thyroid Function Tests (TFTs):
  • For adults where secondary thyroid dysfunction (pituitary disease) is not suspected, consider measuring thyroid-stimulating hormone (TSH) alone ³. If the TSH is above the reference range, free thyroxine (FT4) should be measured from the same sample ³.
  • For children and young people, or adults where secondary thyroid dysfunction is suspected, consider measuring both TSH and FT4 ³.
  • These tests may be repeated if symptoms worsen or new symptoms develop, but no sooner than 6 weeks from the most recent test ³.
• Thyroid Peroxidase Antibodies (TPOAbs):
  • To identify autoimmune thyroiditis, consider measuring thyroid peroxidase antibodies (TPOAbs) for adults with TSH levels above the reference range ³. TPOAbs testing should not be repeated ³.
  • For children and young people with TSH levels above the reference range, TPOAbs should be measured ³.
  • Positive TPOAbs indicate an increased risk of primary hypothyroidism ². They are also associated with an increased risk of a more severe episode of postpartum thyroiditis and a higher likelihood of postpartum hypothyroidism ².