Pitfalls in the measurement and interpretation of thyroid function tests

Area of Science:

• Endocrinology
• Clinical Chemistry
• Laboratory Medicine

Background:

• Thyroid function tests (TFTs) are common investigations.
• Most TFTs are easily interpreted, but some results appear discordant with clinical findings or with each other.

Purpose of the Study:

• To discuss common pitfalls in TFT measurement and interpretation.
• To propose a structured algorithm for managing anomalous or discordant TFT results.

Main Methods:

• Review of clinical context and confounding factors (physiology, illness, medications).
• Screening for laboratory artefacts in immunoassays.
• Consideration of rare disorders of the hypothalamic-pituitary-thyroid axis.

Main Results:

• Discordant TFTs require careful evaluation beyond initial interpretation.
• Confounding factors and assay interferences are common causes of apparent anomalies.
• Rare genetic and acquired disorders of the HPT axis are important considerations in persistent cases.

Conclusions:

• A systematic approach is crucial for accurate diagnosis and management of patients with abnormal TFTs.
• Distinguishing true thyroid dysfunction from assay interference or physiological variations prevents unnecessary interventions.