A practical approach towards the evaluation of aberrant thyroid function tests.

: To provide insight in patterns and causes of aberrant thyroid function tests (TFT) and to propose a practical approach for clinicians.: Starting from an illustrative case report, an extensive literature search was performed, resulting in a narrative literature review.: TFT that cannot be explained by the negative feedback principle of the hypothalamo-pituitary-thyroid axis are a challenge for every clinician.