The Effect of Increased Iodine Intake on Serum Thyrotropin: A Cross-Sectional, Chinese Nationwide Study.

Abstract

Background: Subclinical hypothyroidism is diagnosed based on serum thyrotropin (TSH) reference intervals, which in turn are affected by many factors. Methods: Data were acquired from a Chinese nationally representative cross-sectional study of 78,470 participants (TIDE study). The total study population were participants from the TIDE program, and the reference population was a subset of the total population defined by the National Academy of Clinical Biochemistry (NACB) guidelines. Serum concentrations of thyroid hormones, TSH, thyroid antibodies, and urine iodine concentration (UIC) were measured. Results: The geometric mean serum TSH (2.5th-97.5th) for the reference population (defined by the NACB) and total population was 2.28 mIU/L (0.74-7.04 mIU/L) and 2.34 mIU/L (0.61-8.33 mIU/L), respectively. In the reference population, increase in UIC was significantly associated with increase in the 50th and 97.5th centiles and decrease in the 2.5th centile of TSH. The median TSH was significantly higher in women than in men (2.41 mIU/L vs. 2.16 mIU/L, p-value <0.001). Increased age was significantly associated with an increased TSH, 97.5th centile. For each 10-year increase in the population age, the TSH 97.5th centile increased by 0.534 mIU/L. The prevalence of subclinical hypothyroidism diagnosed according to the assay-recommended interval (Roche 0.27-4.2 mIU/L) and NACB standard interval in the TIDE study (0.74-7.04 mIU/L) differed significantly (Roche 13.61% vs. TIDE 3.00%, p < 0.05). However, there was no significant difference in future cardiovascular disease, reflected by the Framingham risk score, between the 0.27-4.2 and 4.2-7.04 mIU/L TSH groups. Conclusions: Serum TSH concentration significantly increased with increase in iodine intake. Thus, iodine intake must be considered in establishing TSH reference intervals. To avoid overdiagnosis and overtreatment of subclinical hypothyroidism, different areas should use individual serum TSH reference intervals.

• Authors: Lei Zhao, Di Teng, Xiaoguang Shi, Yongze Li, Jianming Ba, Bing Chen, Jianling Du, Lanjie He, Xiaoyang Lai, Yanbo Li, Haiyi Chi, Eryuan Liao, Chao Liu, Libin Liu, Guijun Qin, Yingfen Qin, Huibiao Quan, Bingyin Shi, Hui Sun, Xulei Tang, Nanwei Tong, Guixia Wang, Jin-An Zhang, Youmin Wang, Yuanming Xue, Li Yan, Jing Yang, Lihui Yang, Yongli Yao, Zhen Ye, Qiao Zhang, Lihui Zhang, Jun Zhu, Mei Zhu, Zhongyan Shan, Weiping Teng
• Journal: Thyroid : official journal of the American Thyroid Association (Thyroid) Vol. 30 Issue 12 Pg. 1810-1819 (12 2020) ISSN: 1557-9077 [Electronic] United States
• PMID: 32762331 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Biomarkers
• Thyrotropin
• Iodine

Topics

• Adolescent
• Adult
• Aged
• Asymptomatic Diseases
• Biomarkers (blood)
• China (epidemiology)
• Cross-Sectional Studies
• Diagnostic Errors
• Diet
• Female
• Humans
• Hypothyroidism (blood, diagnosis, epidemiology, therapy)
• Iodine (administration & dosage)
• Male
• Middle Aged
• Predictive Value of Tests
• Prevalence
• Reference Values
• Reproducibility of Results
• Thyrotropin (blood)
• Young Adult