Insufficient iodine nutrition may affect the thyroid cancer incidence in China

Epidemiologic studies have focused on the effects of iodine intake on the risk of thyroid cancer. However, their relationship is still obscure. The objective of this study was to examine the association in the Chinese population. A new ecological study which combined the Annual Report of Cancer, the Survey of Iodine Deficiency Disorder Surveillance and the water iodine survey were conducted to analyze the relationship between iodine intake and the thyroid cancer incidence in China. In total, 281 counties were included. Thyroid cancer incidence was negatively correlated with the consumption rate of qualified iodized salt (CRQIS) and positively correlated with goiter prevalence (GP) of children aged 8˜10 years, residents’ annual income and coastal status. Areas with a low CRQIS and areas with a high GP had a relatively high incidence of thyroid cancer. Regression models showed that a low CRQIS and a high GP in children aged 8˜10 years (both reflecting iodine deficiency status) play a substantial role in thyroid cancer incidence in both males and females. Additionally, living in coastal areas and having a high annual income may also increase the risk of thyroid cancer. These findings suggest that mild iodine deficiency may contribute to the exceptionally high incidence of thyroid cancer in some areas in China. Maintaining appropriate iodine nutrition not only helps to eliminate IDD, but also may help to reduce the occurrence of thyroid cancer.

Change in newly diagnosed Graves’ disease phenotype between the twentieth and the twenty-first centuries: meta-analysis and meta-regression

Purpose According to a few recent studies, the clinical phenotype of Graves’ disease (GD) at onset is becoming milder in recent years, in terms of prevalence and severity of hyperthyroidism, goiter and overt eye disease. The aim of this study was to assess the change in GD phenotype across the late twentieth and the early twenty-first centuries. Materials and methods We carried out a systematic search of studies published between 1/1/1980 and 12/31/2017 describing naïve GD patients at diagnosis. We collected epidemiological, clinical, biochemical and serological data reported in the selected studies, and (1) conducted a single-arm meta-analysis to compare clinical and biochemical characteristics of naïve GD patients before and after year 2000 and (2) performed a meta-regression to identify the trend of the observed clinical presentations. Results Eighty selected articles were related to the period before the year 2000, 30 to the years 2000–2017. According to demographics, the two defined populations were homogeneous at meta-analysis: overall estimated female prevalence was 81% [95% CI 79–82], mean estimated age of the entire population was 39.8 years [95% CI 38.4–41.1], with no significant differences between pre- and post-2000 groups (p > 0.05). The overall estimated prevalence of smokers was 40% [95% CI 33–46], with no significant difference between the two groups (p > 0.05). Mean estimated free thyroxine (FT4) and free triiodothyronine (FT3) levels at diagnosis were higher in the pre-2000 group: 4.7 ng/dl [95% CI 4.5–4.9] for FT4 and 14.2 pg/ml [95% CI 13.3–15.1] for FT3, as compared to the post-2000 group: 3.9 ng/dl [95% CI 3.6–4.2] for FT4 and 12.1 pg/ml [95% CI 11.0–13.3] for FT3 (all p < 0.01). Goiter estimated prevalence was higher in the pre-2000 group, 87% [95% CI 84–90], than in the post-2000 group, 56% [95% CI 45–67]. Estimated prevalence for Graves’ Orbitopathy (GO) was 34% [95% CI 27–41] in the pre-2000 group and 25% [95% CI 19–30] in the post-2000 group (p = 0.03). Accordingly, meta-regression adjusted for covariates showed an average annual reduction of FT4 (− 0.040 ± 0.008 ng/dl, p < 0.0001), FT3 (− 0.316 ± 0.019 pg/ml, p < 0.0001), goiter prevalence (− 0.023 ± 0.008%, p = 0.006), and goiter size (− 0.560 ± 0.031 ml, p < 0.0001). Conclusions Our meta-analysis and meta-regression confirmed that GD phenotype at diagnosis is nowadays milder than in the past; we hypothesize that conceivable factors involved in this change are iodoprophylaxis, worldwide decrease in smoking habits, larger use of contraceptive pill and micronutrient supplementation, as well as earlier diagnosis and management.

Iodine deficiency disorders in a South Indian district: still a public health problem?

Background: Iodine deficiency disorders (IDD) constitute the single largest cause of preventable brain damage worldwide leading to learning disabilities and psychomotor impairment. Nearly 266 million school children worldwide have insufficient iodine intake. IDD was found to be a public health problem in 47 countries. Since the information on current prevalence of goiter in Kolar was not available, the present study was undertaken.Methods: A cross-sectional study was conducted among school children aged 6-12 years in Kolar taluk. A total of 2700 children were selected for goiter examination by multistage random cluster sampling technique. A total of 270 children were tested for the median urinary concentration and 540 salt samples were tested from the households of the study population.Results: The total goiter rate was 5.66% among primary school children aged 6-12 years with a significant difference between ages. As the age increased the goiter prevalence also increased. The median urinary iodine excretion level was found to be 105 mcg/l and 92.788.7% salt samples had >15 ppm iodine content.Conclusions: Present study shows mild goiter prevalence in primary school children in Kolar district and an adequate iodine content of salt in urine.

Association of Cassava Consumption with Median Urinary Iodine Concentrations and Goiter Prevalence: A Pooled Analysis of 176 Countries

Objectives Despite the universal iodization of salt in most parts of the world, iodine deficiency disorder remains a major public health problem, affecting over 2 billion people. Published literature on the association of over-consumption of cassava (a goitrogenic food) with lower urinary iodine concentration (UIC) and increased goiter prevalence are inconsistent. We aimed to examine the association of country-level cassava consumption with country-level median urinary iodine concentrations and goiter prevalence. Methods We analyzed data on cassava consumption (kcal/capita/day) from the food and agriculture organization (FAO), median UIC, and goiter prevalence from the World Health Organization for 176 countries. We adjusted for country-level salt iodization rates. Meta-regression analysis was used to estimate the association of cassava consumption with median UIC and goiter prevalence. Results The median UIC was: 171 μg/L; 25th and 75th percentile: 119–220). Median cassava consumption was 114 kcal/capita/day (25th and 75th percentile: 22–284). In the pooled multivariable-adjusted analysis, a 10-fold increase in salt iodization rate was significantly associated with a 157% increase in median UIC (β = 15.7, P = 0. 009. We found no association between cassava consumption and median UIC (β = −0.01, P = 0.90) or goiter prevalence (β = −0.005, P = 0.75). We consistently found no association between cassava consumption and the aforementioned outcomes in the subgroup of low and middle-income countries versus high-income countries and the lagged year of cassava consumption. Conclusions In this ecological study, the consumption of iodized salt was associated with higher median UIC. We found no association of cassava consumption with reduced median UIC or increased goiter prevalence. Funding Sources None.

Assessment of the iodine nutritional status among Chinese school-aged children

Objective The remarkable success of iodine deficiency disorders (IDD) elimination in China has been achieved through a mandatory universal salt iodization (USI) program. The study aims to estimate the relationship between urinary iodine concentration (UIC) and iodine content in edible salt to assess the current iodine nutritional status of school aged children. Methods A total of 5565 students from 26 of 39 districts/counties in Chongqing participated in the study, UIC and iodine content in table salt were measured. Thyroid volumes of 3311 students were examined by ultrasound and goiter prevalence was calculated. Results The overall median UIC of students was 222 μg/L (IQR: 150-313 μg/L). Median UIC was significantly different among groups with non-iodized salt (iodine content <5 mg/kg), inadequately iodized salt (between 5 and 21 mg/kg), adequately iodized (between 21 and 39 mg/kg) and excessively iodized (>39 mg/kg) salt (P < 0.01). The total goiter rate was 1.9% (60/3111) and 6.0% (186/3111) according to Chinese national and WHO reference values, respectively. Thyroid volume and goiter prevalence were not different within the three iodine nutritional status groups (insufficient, adequate and excessive, P > 0.05). Conclusions The efficient implementation of current USI program is able to reduce the goiter prevalence in Chongqing as a low incidence of goiter in school aged children is observed in this study. The widened UIC range of 100–299 μg/L indicating sufficient iodine intake is considered safe with a slim chance of causing goiter or thyroid dysfunction. Further researches were needed to evaluate the applicability of WHO reference in goiter diagnose in Chongqing or identifying more accurate criteria of normal thyroid volume of local students in the future.

A study of prevalence of goiter among school children in Kolar

Background: Iodine deficiency disorders (IDD) constitute the single largest cause of preventable brain damage worldwide leading to learning disabilities and psychomotor impairment. Nearly 266 million school children worldwide have insufficient iodine intake. IDD was found to be a public health problem in 47 countries. Since the information on current prevalence of goiter in Kolar was not available, the present study was undertaken.Methods: A cross-sectional study was conducted among school children aged 6-12 years in Kolar taluk. A total of 650 children (325 urban and 325 rural) were selected for goiter examination by multistage random cluster sampling technique. A total of 150 children were tested for the median urinary concentration and 150 salt samples were tested from the households of the study population.Results: The total goiter rate was 6.6% among primary school children aged 6-12 years with a significant difference between ages. As the age increased the goiter prevalence also increased. The median urinary iodine excretion level was found to be 137 µg/l and 92.7% salt samples had >15 ppm iodine content.Conclusions: Present study shows mild goiter prevalence in primary school children in Kolar and an adequate iodine content of salt and urine.

Agreement between markers of population iodine status in classifying iodine status of populations: a systematic review

ABSTRACT Background Population iodine deficiency is indicated by >3% of the population with newborn thyroid-stimulating hormone (TSH) concentration >5 mIU/L, median urinary iodine concentration (MUIC) <100 µg/L, or >5% prevalence of goiter in school-age children. However, the agreement between these population markers has not been systematically investigated. Objective To assess the agreement between TSH, MUIC, and goiter as markers of population iodine status. Methods We performed a systematic search for studies published on PubMed, Scopus, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Embase, and PsycINFO up to 29 October, 2018. Studies assessing iodine status in the population using the TSH marker and either MUIC or goiter prevalence in school-age children were included. The agreement between markers in classifying iodine status of the population was assessed. The sensitivity and specificity of the TSH marker was determined against MUIC and goiter prevalence as the reference markers. Results Of 17,435 records identified by the search strategy, 57 eligible studies were included in the review. The agreement between markers in classifying the iodine status of populations into the same category was 65% for TSH and MUIC, and 83% for TSH and goiter prevalence. The TSH marker had a sensitivity of 0.75 and specificity of 0.53 when compared with MUIC, and 0.86 and 0.50 when compared with goiter prevalence. Conclusions The TSH marker has a better agreement with goiter prevalence than MUIC when classifying the iodine status of populations. Re-evaluation of the current criteria for classifying the iodine status of populations using the TSH marker is warranted. This systematic review was registered at PROSPERO (http://www.crd.york.ac.uk/prospero/) as CRD42018091247.

Socioeconomic status of the population – a prime determinant in evaluating iodine nutritional status even in a post salt iodization scenario

Background To compare the state of iodine nutrition among school age children (SAC) in high- (HSGs) and low-socioeconomic groups (LSGs) during a post iodation scenario in Kolkata. Methods Clinical examinations of the goiter, median urinary iodine (MUI), mean urinary thiocyanate (MUSCN) in SAC (6–12 years) from both sexes in the different socioeconomic groups were carried out and the iodine content of edible salt was measured. Results A total of 5315 SAC, of which 2875 SAC were from a HSG and another 2440 SAC from an LSG were clinically examined for goiter. In the HSGs the total goiter prevalence (TGP) was 3.2% and in the LSGs the TGP was 9.1% and the difference was statistically significant (p<0.001). The MUI of the HSGs was 242 μg/L as compared to 155 μg/L in the LSGs (p<0.001). MUSCN of the HSGs was 0.77±0.45 mg/dL while in the LSGs it was 0.94±0.44 mg/dL and the difference was statistically significant (p<0.01). In the HSGs 19.4% salt samples had 15–30 ppm iodine and 80.6% salt samples were above 30 ppm as compared to 26.3% salt samples which were below 15 ppm, 37.1% salt samples which were between 15 and 30 ppm and 36.6% salt samples which were above 30 ppm in the LSGs. Conclusions The population of the LSGs was clinically mildly iodine deficient having no biochemical iodine deficiency while in the HSGs it was more than the adequate requirement and the HSG children are possibly at risk of excess iodine induced thyroid diseases. Existing goiter prevalence in the LSGs was from their relatively high consumption of dietary goitrogens. Therefore, socioeconomic status plays a pivotal role in the management of iodine nutrition even in a post salt iodation scenario.

The effect of 17 years of increased salt iodization on the prevalence and nature of goiter in Croatian schoolchildren

Background High goiter prevalence caused by iodine deficiency (medium content 5.6 mg potassium iodide [KI]/kg of salt, median urine iodine concentration [UIC] 68 μg/L) in Croatia was observed in 1991 and 1995 when salt was iodized with 10 mg KI/kg. A new regulation introduced in 1996, specified 25 mg KI/kg of salt resulting in an increase of median UIC to 248 μg/L. Afterwards, goiter prevalence was only assessed in two small studies. Methods In this study, we investigated the prevalence and etiology of goiter in 3594 schoolchildren 17 years after an increase in salt iodization in Croatia. Thyroid size was determined by palpation in 1777 girls and 1817 boys aged 10–18 years. In goitrous children, a thyroid ultrasound and thyroid-stimulating hormone, free thyroxine (fT4), free triiodothyronine (fT3), thyroid peroxidase (TPO) and thyroglobulin (TG) antibody measurements were performed. Results Goiter was found in 32 children (0.89% vs. 2.8% in 1991, p<0.00001 and 27% in 1995, p<0.00001), simple goiter (SG) in 18/32 (56%) goitrous children vs. 126/152 (82.8%) in 1991 p<0.00001, autoimmune thyroiditis (AT) in 13/32 (40.6%) vs. 19/152 (12.5%) in 1991 p<0.0009, nodules in four: two cysts, toxic adenoma and carcinoma (in 1991 two adenomas and one cyst), Graves’ disease was not found (four in 1991). Subclinical hypothyroidism was found in three children. Thyroid disease was diagnosed in four of 32 children before the investigation. Increased iodine supply decreased goiter prevalence and SG/AT ratio in goitrous patients. Conclusions As thyroid abnormalities were found in 0.89% of children and some required treatment, thyroid examination is important in apparently healthy children regardless of sufficient iodization.