Serum thyroid hormone reference intervals in the apparently healthy individuals of Zhengzhou area of China

This study aimed to establish reference intervals for serum thyroid hormones [serum thyroid-stimulating hormone (TSH), triiodothyronine (TT3), thyroxine (TT4), free triiodothyronine (FT3), and free thyroxine (FT4)] in apparently healthy individuals living in Zhengzhou. According to the requirement for laboratory support for the diagnosis and monitoring of thyroid diseases in the National Academy of Clinical Biochemistry (NACB) laboratory medicine practice guidelines, a total of 211 apparently healthy individuals were enrolled (94 men, 117 women, 23-77 years old) from Zhengzhou for measurement of serum levels of TSH, TT3, TT4, FT3, and FT4 by using the Siemens ADVIA Centaur XP analyzer. All markers were analyzed across gender-and age-specific groups by using the t-test and ANOVA. The reference intervals of all markers were determined by P-2.5-P-97.5. We detected gender-associated statistical significances for TT3, TT4, FT3, and FT4 (t = 3.299, 2.141, 5.868, 5.358; P < 0.05), but not for TSH (t = -1.776, P > 0.05). Correlation analysis showed that all markers were negatively correlated with age (P > 0.05). The new reference intervals for TT3, TT4, FT3, FT4, and TSH were established: 0.76-1.38 ng/mL, 5.96-11.27 mu g/dL, 3.88-5.59 pM, 11.69-18.84 pM, 0.89-5.93 mu IU/mL, respectively. In conclusion, we added a new database of reference intervals of the serum thyroid hormones for the Chinese adult population.