Endocrine Abstracts

Thyroid dysfunction is common, and thyroid function tests (TFTs) are amongst the most frequently requested laboratory measurements, both in the adult and paediatric setting. Fortunately, most TFTs are straightforward to interpret and confirm a clinical diagnosis of eu-, hypo- or hyperthyroidism. In most cases, the underlying cause of thyroid dysfunction is readily apparent from clinical findings and standard investigations (e.g. antibody testing, radionuclide scan). In a subset of cases, the cause of thyroid dysfunction can be elusive and/or TFT results can be confusing- either being discordant with the clinical picture or appearing to be incongruent with each other. Causes to consider in such settings include non thyroidal illness, assay interference, genetic disorders (Resistance to Thyroid Hormone alpha or beta, familial dysalbuminaemic hyperthyroxinaemia and others) or environmental causes (e.g. iodine deficiency). In this case-based session, my approach to such patients will be discussed, with particular emphasis on differentiating between possibilities such as assay interference and rare thyroid disorders (such as Resistance to Thyroid Hormone). I will also provide a practical algorithm to the initial investigation and further work up of such patients.