Diagnosing thyroid disease: pitfalls and improvement in laboratory measurements

The aim of this thesis was to evaluate and improve laboratory measurements in diagnosing thyroid disease. This thesis demonstrates the extensive scope of laboratory measurements in diagnosing thyroid disease and its tendency towards a more personalized diagnostic approach. In the first part, we provided better insight into the performance of the current free thyroxine (fT4) immunoassays in specific populations. In the second part, we described newly developed liquid chromatography tandem-mass spectrometry (LC-MS/MS) methods to measure fT4, total T4, total triiodothyronine (T3), and reverse T3 (rT3). The third part shed light on thyroid disease diagnostics and proposed and developed improvements in this diagnostic process. Clinicians are not always aware of possible drawbacks of laboratory measurements. However, this thesis shows it is worth diving into this important part, with a focus on thyroid disease diagnostics as it can have major clinical consequences. Collaboration between laboratory specialists and requesting medical specialists is thus vital for achieving optimal thyroid care.