Relationship between urinary iodine and goiter prevalence: results of the Chinese national iodine deficiency disorders survey.

ABSTRACT

BACKGROUND: In 1984, Yu Zhiheng proposed the "U-curve" regularity between urinary iodine (UI) and goiter prevalence (GP). However, along with the adjustment of salt iodine and iodine deficiency disorders (IDD), and surveys followed, some defects were found in the research. As a result, it is time to test and enrich the theory as a series of large sample survey data from China would be helpful. AIM: To test and enrich the theory of "U-curve" relationship between UI and GP. SUBJECTS AND METHODS: Based on the Chinese national IDD surveys (1999, 2002, 2005), the High Water Iodine survey of 2005, and the High Risk endemias survey of 2007, this article analyzed the relationship between UI and GP. The UI was grouped according to the World Health Organization (WHO) standard, self-defined (5 microg/l), and Yu Zhiheng's level, separately, the GP was calculated for population with different UI level, the tendency curve was drawn and the fitting curve model was estimated by SPSS. RESULTS: For the 2005 Chinese national survey and 2005 High Water Iodine survey, we finally got the fitting curves and corresponding UI reference limits. CONCLUSIONS: The UI and GP formed a "U curve" relationship. It varied with some reasons and fell into an accurate U shape step by step. For High Water Iodine endemias survey, the relationship changed to "power curve". Regarding the WHO recommended GP<5%, the UI range of school-age children in normal district should be 110-315 microg/l, whereas, in high water iodine district should be <80 microg/l.