1 INTRODUCTION Thyroid dysfunction affects 2%–5% of the global population and is readily diagnosed with modern sensitive laboratory tests of thyroid function.1 Query of the national laboratory information system (LIMS) revealed one million thyroid function tests (TFTs) comprising FreeT4 (FT4) and TSH were undertaken in our laboratories in Wales in 2019, a country with an approximate population of 3 million people.2 At the time, the testing strategy for the diagnosis of thyroid dysfunction in...
