[TSH-reference range of adults: results from the population-based study KORA F4].

INTRODUCTION: There is no valid nationwide reference value for Thyroid-stimulating hormone (TSH) for German adults because of different iodine supply and different laboratory equipment, however, reference values for single regions of Germany have been defined. The aim of this study was to find a reference value for South Germany and to compare this with results of other population-based studies.

METHODS: 3080 individuals from the KORA-F4 study (Cooperative Health Research in the Region of Augsburg) at the age range of 32 to 81 years were examined regarding their thyroid characteristics (anamnesis, sonography and clinical chemistry). After excluding individuals with known as well as unknown thyroid disorders revealed by the KORA study, there were 710 thyroid-healthy individuals left to evaluate TSH-, fT3- and fT4-reference ranges.

RESULTS: For thyroid-healthy men and women we evaluated a TSH-reference range of 0.52-3.60 mIU/l on Siemens Vista Analysers with a median of 1.49 mIU/l. We could not find any statistically significant influence of age or sex. Median iodine excretion in urine was 118.6 µg/g creatinine in our healthy population which is above the recommended target value of 100 µg/g.

DISCUSSION: The TSH-reference value of the South German population is higher than the one assessed in the Northeast-German SHIP-study 10 years ago. For the definition of a TSH-reference value, population-based and apparatus-specific examinations are necessary.