thyroid disease diagnostic algorithm

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Where TSH and free T3 or T4 are measured as the first-line thyroid investigation there are six patterns of abnormality:

  • TSH may be high or low
  • free T3 or free T4 may be low, normal or high


  • Dayan CM. Interpretation of thyroid function tests. Lancet 2001;357:619-24.

Last edited 04/2021 and last reviewed 06/2021