Endocrine Abstracts

Introduction: Physicians in our hospital notified the laboratory staff of a number of patients at the outpatient clinic with increased free T4 (fT4) concentrations without (complete) suppression of thyroid stimulating hormone (TSH). This phenomenon appeared to occur more frequently following implementation of a new automated fT4 immunoassay. The discordance between fT4 and TSH concentrations may be explained by analytical issues (not further explained here), incorrect referenc...

Objectives: Free thyroxine (fT4) measurements are performed to detect thyroid disorders and monitor treatment. FT4 is measured using automated immunoassays (IAs) which face established analytical challenges due to low serum concentrations in the picomolar range and the precarious equilibrium between free and bound T4 (to thyroid-binding globulin (TBG) and (pre-)albumin). Furthermore, IAs are known to be affected by the composition of the serum sample (matrix-effects), which ca...

Objectives: Congenital hypothyroidism (CH) is an inborn thyroid hormone (TH) deficiency mostly caused by disturbances at the thyroid level (thyroidal CH, CH-T). Less frequently, but equally important, CH can be the result of hypothalamic/pituitary dysfunction (central CH, CH-C). Most CH newborn screening (NBS) programs are based on the measurement of thyroid-stimulating hormone (TSH), thereby only detecting CH-T. The Dutch NBS detects CH by measuring total T4 concentrations in...

Introduction: Thyroid disorders are generally diagnosed based on thyroid stimulating hormone (TSH) outside the reference interval (RI), and subsequent free thyroxine (FT4) concentrations. Most laboratories do not provide age-specific RIs for TSH and FT4 beyond childhood, although it is known that TSH concentrations vary with age which may be important to take into account. Therefore, we aimed to establish age-specific RIs for TSH and FT4 throughout life using an indirect metho...