Searchable abstracts of presentations at key conferences in endocrinology
Endocrine Abstracts (2014) 35 S26.2 | DOI: 10.1530/endoabs.35.S26.2

ECE2014 Symposia Pitfalls in hormone measurement (3 abstracts)

Pitfalls in the measurement and interpretation of thyroid function tests

Mark Gurnell 1,


1University of Cambridge, Cambridge, UK; 2Addenbrooke’s Hospital, Cambridge, UK.


Accurate diagnosis of thyroid dysfunction is dependent on understanding hypothalamic–pituitary–thyroid (HPT) axis physiology and the pathophysiology that can affect this classical endocrine feedback loop. Even minor perturbations of thyroid status, which may be imperceptible to the patient and clinician, can significantly alter the relationship between circulating thyroid hormone (TH) levels and pituitary TSH such is the finely-tuned nature of the axis.

Thyroid function tests (TFTs) are amongst the most commonly requested laboratory investigations in both primary and secondary care. Fortunately, most TFTs are straightforward to interpret and confirm the clinical impression of euthyroidism, hypothyroidism, or hyperthyroidism. However, in an important subgroup of patients the results of TFTs can seem confusing, either by virtue of being discordant with the clinical picture or because they appear incongruent with each other (e.g. raised TH but with non-suppressed TSH; raised TSH, but with normal TH). In such cases, it is important first to revisit the clinical context, and to consider potential confounding factors, including alterations in normal physiology (e.g. pregnancy), intercurrent (non-thyroidal) illness, and medication usage (e.g. thyroxine, amiodarone and heparin). Once these have been excluded, laboratory artefact in commonly used TSH or TH immunoassays should be screened for, thus avoiding unnecessary further investigation and/or treatment in cases where there is assay interference. In the remainder, consideration should be given to screening for rare genetic and acquired disorders of the HPT axis (e.g. resistance to thyroid hormone (RTH) and thyrotropinoma (TSHoma)).

In this session, I will discuss the main pitfalls in the measurement and interpretation of TFTs, and propose a structured algorithm for the investigation and management of patients with anomalous/discordant TFTs.

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