Prevalence of Goiter and Thyroid Nodules before and after Implementation of the Universal Salt Iodization Program in Mainland China from 1985 to 2014: A Systematic Review and Meta-Analysis

Abstract

ObjectivesWe comprehensively estimated the prevalence of goiter and thyroid nodules (TNs) before and after the implementation of the Universal Salt Iodization (USI) program in mainland China and provided information for creating effective health policies.MethodsPubMed, Google Scholar, CNKI, Chinese Wanfang and Chongqing VIP databases were searched for relevant studies from Jan 1985 to Feb 2014. Data from eligible citations were extracted by two independent reviewers. All analyses were performed with Stata 11.0 and SPSS 17.0.ResultsEligible articles (N = 31; 4 in English and 27 in Chinese) included 52 studies (15 about goiter rates made before 1996 and 14 afterwards, and 23 about TNs). Our meta-analysis suggests a pooled prevalence for goiter before and after 1996 and for TNs of 22.8% (95% CI: 15.3%, 30.3%), 12.6% (95% CI: 9.4%, 15.8%) and 22.7% (95% CI: 18.3%, 27.0%), respectively. Egger's test of three independent categories revealed no evidence of publication bias (p = 0.101, 0.148 and 0.113, respectively).ConclusionsThe prevalence of goiter was reduced by almost half after 1996 in mainland China, so the USI program was considered beneficial. However, subgroup analysis suggests that both insufficient and excess iodine may be associated with goiter. The prevalence of goiter and TNs increased significantly after 2002, suggesting a risk of excessive iodine intake. Thus, salt iodization standardizations should be set according to local conditions.

Prospective study of seaweed consumption and thyroid cancer incidence in women

“…However, to our knowledge, other studies did not find associations of dietary iodine intake from edible seaweed or supplements with thyroid cancer incidence (Kolonel et al, 1990;Horn-Ross et al, 2001;Zhang et al, 2013). Although ecological studies observed increased thyroid cancer incidence in Denmark (Blomberg et al, 2012) and China (Zhao et al, 2014) after the implementation of compulsory iodine supplementation, such studies could be susceptible to detection bias related to thyroid cancer screening of asymptomatic individuals and improvement in diagnostic modalities (Ahn et al, 2014;La Vecchia et al, 2015). In sum, it is inconclusive whether excessive iodine intake is harmful or not, although the present study did not suggest such an effect.…”

Reference intervals of thyroid hormones in a previously iodine-deficient but presently more than adequate area of Western China: a population-based survey

“…However, in 2013 it was reported that the MUI of school-age children in Xi'an was 280.5 μg/L [8], higher than the standard levels proposed by World Health Organization (WHO) [9], indicating that the iodine intake of population in Xi'an was more than adequate. Actually, many inland areas of China have experienced the similar conversion from iodine-deficiency to iodine-sufficiency or more than adequacy during the past two decades [10], which necessitates the establishment of accurate RIs. More importantly, although China has three RIs of thyroid hormones so far, the three RIs were all from hospital-or communitybased studies or from studies not excluding patients with abnormal ultrasonography findings [11][12][13].…”

Evaluation the Relationship Between Thyroid Nodule Size with Malignancy and Accuracy of Fine Needle Aspiration Biopsy (FNAB)

“…For example this prevalence is from 8 to 65% in autopsy and from 19 to 35% in ultrasound survey (2). According to retrospective studies, only 4-5% of thyroid nodules are malignant (3)(4)(5). Several risk factors have been reported for the presence of carcinoma in thyroid nodules, and one of them is the size of the thyroid nodules (6).…”