Relationship between water iodine and children’s goiters

Excessive iodine can lead to goiters. However, the relationship between the water iodine concentration (WIC) and goiter rate (GR) is unclear. This study aims to explore the factors that influence children’s GR in areas with high WIC and analyse the threshold value of the GR increase associated with the WIC. According to the monitoring of the areas with high WIC in China in 2018–2020, a total of 54,050 children in eight high water iodine provinces were chosen. Drinking water, urine and edible salt samples of children were collected. The thyroid volume (Tvol) was measured. A generalized additive model (GAM) was used to analyse the relationship between the WIC and GR in children. Among the 54,050 children in areas with high WIC, the overall GR was 3.34%, the median of water iodine concentration (MWIC) was 127.0 µg/L, the median of urinary iodine concentration (MUIC) was 318 µg/L, and the noniodized salt coverage rate (NISCR) was 63.51%. According to the GAM analysis results, water iodine and urinary iodine are factors that influence the Tvol and GR, while the NISCR affects only the GR. When the WIC was more than 420 µg/L or the urinary iodine concentration (UIC) was more than 800 µg/L, the GR increased rapidly. When the NISCR reached more than 85%, the GR was the lowest. Thus, in areas with high WIC, WIC more than 420µg/L may increase the risk of goiter, and the NISCR should be increased to over 85% to avoid goiters in children.

Evaluation of iodine nutritional status during pregnancy by estimated 24-hour urinary iodine excretion: population variation range and individual accuracy

Objective: To explore the accuracy of estimated 24-hour urinary iodine excretion(24hUIEest) in assessing iodine nutritional status. Design: Fasting venous blood, 24-hour and spot urine samples were collected during the day. The urinary iodine concentration (UIC) and urinary creatinine concentration (UCrC) were measured, and the urinary iodine-to-creatinine ratio (UI/Cr), 24hUIEest, and 24-hour urinary iodine excretion(24hUIE) were calculated. At the population level, correlation and consistency between UIC, UI/Cr, 24hUIEest and 24hUIE were assessed using correlation analysis and Bland-Altman plots. At the individual level, ROC curves were used to analyse the accuracy of the above indicators for evaluating insufficient and excessive iodine intake. The reference interval of 24hUIEest was established based on percentile values. Setting: Indicator can accurately evaluate individual iodine nutrition during pregnancy remains controversial. Participants: Pregnant women (n=788). Results: Using 24hUIE as standard, the correlation coefficients of 24hUIEest from different periods of the day ranged from 0.409 to 0.531, and the relative average differences ranged from 4.4% to 10.9%. For diagnosis of insufficient iodine intake, the area under the ROC curve of 24hUIEest was 0.754, sensitivity and specificity were 79.6% and 65.4%, respectively. For diagnosis of excessive iodine intake, the area of 24hUIEest was 0.771, sensitivity and specificity were 66.7% and 82.0%, respectively. The reference interval of 24hUIEest was 58.43-597.65μg. Conclusions: 24hUIEest can better indicate iodine nutritional status at a relatively large sample size in a given population of pregnant women. It can be used for early screening at the individual level to obtain more lead time for pregnant women.

Effects of iodine excess on serum thyrotropin-releasing hormone levels and type 2 deiodinase in the hypothalamus of Wistar rats

Iodine is an important element in thyroid hormone biosynthesis. Thyroid function is regulated by the hypothalamic-pituitary-thyroid axis (HPT). Excessive iodine leads to elevated thyroid stimulating hormone (TSH) levels, but the mechanism is not yet clear. Type 2 deiodinase (Dio2) is a selenium-containing protease that plays a vital role in thyroid function. The purpose of this study was to explore the role of hypothalamus Dio2 in regulating TSH increase caused by excessive iodine and to determine the effects of iodine excess on thyrotropin-releasing hormone (TRH) levels. Male Wistar rats were randomized into five groups and administered different iodine dosages (folds of physiological dose): normal iodine (NI), 3-fold iodine (3HI), 6-fold iodine (6HI), 10-fold iodine (10HI), and 50-fold iodine (50HI). Rats were euthanized at 4, 8, 12, or 24 weeks after iodine administration. Serum TRH, TSH, total thyroxine (TT4), and total triiodothyronine (TT3) were determined. Hypothalamus tissues were frozen and sectioned to evaluate expression of Dio2, Dio2 activity, and monocarboxylate transporter 8 (MCT8). Prolonged high iodine intake significantly increased TSH expression (p < 0.05), but did not affect TT3 and TT4 levels. Prolonged high iodine intake decreased serum TRH levels in the hypothalamus (p < 0.05). Dio2 expression and activity in the hypothalamus exhibited an increasing trend compared at each time point with increasing iodine intake (p < 0.05). Hypothalamic MCT8 expression was increased in rats with prolonged high iodine intake(p < 0.05). These results indicate that iodine excess affects the levels of Dio2, TRH, and MCT8 in the hypothalamus.

Hyperthyroidism Prevalence in China After Universal Salt Iodization

BackgroundUniversal salt iodization (USI) was implemented in mainland China in 1996. The prevalence of hyperthyroidism and its risk factors now require examination.MethodsData were acquired from a nationwide Thyroid, Iodine, and Diabetes Epidemiological survey (TIDE 2015–2017) of 78,470 subjects from 31 provinces. Iodine status, and thyroid hormones and antibodies were measured. ResultsAfter two decades of USI, the prevalence of overt hyperthyroidism (OH), Graves’ disease (GD), severe subclinical hyperthyroidism (severe SCH), and mild subclinical hyperthyroidism (mild SCH) in mainland China was 0.78%, 0.53%, 0.22%, and 0.22%, respectively. OH and GD prevalence were higher in women than in men (OH: 1.16% vs. 0.64%, P&lt;0.001; GD: 0.65% vs. 0.37%, P&lt;0.001).Prevalence was significantly decreased after 60 years-of-age compared with 30–39 years-of-age (OH:0.61% vs. 0.81%, P&lt;0.001; GD: 0.38% vs. 0.57%, P&lt;0.001).Excessive iodine(EI) and deficient iodine(DI) were both related to increased prevalence of OH (odds ratio [OR] 2.09, 95% confidence interval [CI] 1.68–2.59; OR1.35, 95%CI 1.07–1.72, respectively); however, only deficient iodine was associated with increased prevalence of GD (OR1.67, 95%CI 1.30–2.15). Increased thyroid peroxidase antibody and thyroglobulin antibody levels were significantly associated with prevalence of OH and GD, but not severe SCH and mild SCH. Although hyperthyroidism was more prevalent in women, the association disappeared after adjusting for other factors such as antibody levels.ConclusionOH and GD prevalences in mainland China are stable after two decades of USI. Iodine deficiency, elevated thyroid antibody levels, and middle age are the main risk factors for OH and GD. The severe SCH population, rather than the mild SCH population, shows similar characteristics to the OH population.

Excessive Prenatal Supplementation of Iodine and Fetal Goiter: Report of Two Cases Using Three-dimensional Ultrasound and Magnetic Resonance Imaging

Fetal thyroid complications in pregnancy are uncommon, and are commonly related to the passage of substances through the placenta. The excessive iodine intake during the pregnancy is a well-known mechanism of fetal thyroid enlargement or goiter, and invasive procedures have been proposed for the treatment of fetal thyroid pathologies. In the present report, we demonstrate two cases from different centers of prenatal diagnosis of fetal thyroid enlargement and/or goiter in three fetuses (one pair of twins, wherein both fetuses were affected, and one singleton pregnancy). The anamnesis revealed the ingestion of iodine by the patients, prescribed from inadequate vitamin supplementation. In both cases, the cessation of iodine supplement intake resulted in a marked reduction of the volume of the fetal thyroid glands, demonstrating that conservative treatment may be an option in those cases. Also, clinicians must be aware that patients may be exposed to harmful dosages or substances during pregnancy.

Excessive Iodine Induces Thyroid Follicular Epithelial Cells Apoptosis by Activating HIF-1α-mediated Hypoxia Pathway in Hashimoto Thyroiditis

Purpose Hashimoto thyroiditis (HT) is considered the most common autoimmune thyroid disease. A growing body of evidence suggests that HT incidence correlates with excessive iodine intake. We should probe the effects of excessive iodine intake in HT development and its possible mechanism. Methods The study recruited 20 patients: 10 with HT and 10 with nodular goiter. We detected the expression of an apoptosis-related protein caspase-3 by immunohistochemistry. In vitro study, we explored the proliferation and apoptosis status in thyroid follicular cells (TFCs) stimulated at different iodine concentrations by MTT and flow cytometry. Then we performed RNA sequence analysis of Nthy-ori3-1 cells treated for 48h with different KI concentrations to probe the underlying mechanism. Finally, we used RT-PCR to verify its results. Results We identified apoptosis in thyroid tissue obtained from HT patients coincides with the increase of caspase-3 levels. In vitro study, iodine suppressed proliferation of TFCs and promoted TFCs apoptosis in a dose-dependent manner. RNA sequence results showed that high concentration of iodine activate the hypoxia-inducible factor-1α (HIF-1α)-mediated hypoxia pathway coincide with the upregulation of N-myc downregulated gene-1 (NDRG1) expression. Conclusions Our study confirmed that excessive iodine adsorption activates the HIF-1α-mediated hypoxia pathway to promote apoptosis of TFCs, which may be an important risk factor contributing to HT development.

Establishment of an iodine model for prevention of iodine-excess-induced thyroid dysfunction in pregnant women

This study aims to explore the relationship between the iodine status and thyroid dysfunction (TD) in pregnant women and establish a model to guide them to prevent excessive iodine intake. A total of 515 pregnant women were enrolled in the study. Urinary iodine concentration (UIC), thyroid hormones, and thyroid autoantibodies were measured, and then a logistic regression model was established. The median UIC of pregnant women was 174 ± 120 μg/L. Multivariate logistic regression analysis indicated that multivitamin supplements containing iodine and frequent seafood consumption were risk factors for excessive iodine (UIC ≥500 μg/L). Besides, excessive iodine was a risk factor for TD. Iodine excess was associated with a high prevalence of TD in pregnant women, especially TPOAb-positive women (P < 0.05). A logistic regression model based on potential risk factors was established to predict the risk of excessive iodine intake among pregnant women and provide guidance to minimize the risk of excessive iodine intake, thus reducing the risk of TD.

Iodine Status and Thyroid Function in a Group of Seaweed Consumers in Norway

Seaweeds, or macroalgae, may be a good dietary iodine source but also a source of excessive iodine intake. The main aim in this study was to describe the iodine status and thyroid function in a group of macroalgae consumers. Two urine samples were collected from each participant (n = 44) to measure urinary iodine concentration (UIC) after habitual consumption of seaweed. Serum thyroid stimulating hormone (TSH), free thyroxine (fT4), free triiodothyronine (fT3), and peroxidase autoantibody (TPOAb), were measured in a subgroup (n = 19). A food frequency questionnaire and an iodine-specific 24 h recall were used to assess iodine intake and macroalgae consumption. The median (p25–p75) UIC was 1200 (370–2850) μg/L. Median (p25–p75) estimated dietary iodine intake, excluding macroalgae, was 110 (78–680) μg/day, indicating that seaweed was the major contributor to the iodine intake. TSH levels were within the reference values, but higher than in other comparable population groups. One third of the participants used seaweeds daily, and sugar kelp, winged kelp, dulse and laver were the most common species. Labelling of iodine content was lacking for a large share of the products consumed. This study found excessive iodine status in macroalgae consumers after intake of dietary seaweeds. Including macroalgae in the diet may give excessive iodine exposure, and consumers should be made aware of the risk associated with inclusion of macroalgae in their diet.