Abstract: Objective To investigate serum thyroid stimulating hormone (TSH) level and its changes with age in apparently healthy Chinese elderly population and analyze the differences between TSH levels detected using Roche and Snibe electrochemiluminescence immunoassay analyzers. Methods General clinical data and frozen fasting serum samples were collected from 5451 apparently healthy Chinese elderly individuals (>60 years) from 10 centers in different geographic regions in China. Thyroid function indexes including TSH level were detected using Roche and Snibe electrochemiluminescence immunoassay analyzer, and the median (2.5% and 97.5% quantiles) TSH level was calculated. The variations of TSH level among the participants with geographic regions, gender, and age (with an interval of 5 years) were analyzed to determine the influence of these factors on TSH level. Results The reference ranges of serum TSH level established using Roche and Snibe electrochemiluminescence immunoassay analyzers were 0.42-9.47 mU/L and 0.36-7.98 mU/L, respectively, showing significant differences between the two methods (P<0.001). The TSH levels measured at two centers in Western China were significantly higher than those at the other centers (P<0.05). In elderly male population, serum TSH level tended to increase with age, which was not observed in elderly female population. At the age of 60-75 years, women generally had higher serum TSH level than men, but this difference was not observed in the population beyond 75 years. Conclusion In elderly population, serum TSH level can vary with geographic region, gender, and age, but there was no need for establishing specific reference ranges for these factors. The differences between different detection methods should be evaluated when interpreting the detection results of TSH level.

Key words: thyroid-stimulating hormone; elderly population; reference range; gender