2024: Effects of high fluoride and iodine combined exposure on thyroid nodules and goiter in school-age children

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Xia Y, Ye Y, Liu M, Wang Y, Shang L, Wang P, Xu Y - "Effects of high fluoride and iodine combined exposure on thyroid nodules and goiter in school-age children in Jiangsu, China" Heliyon 10(21):e40082 (2024)
https://doi.org/10.1016/j.heliyon.2024.e40082

• Note: The 711 children in this study are the exact same cohort evaluated for the relationship between fluoride and IQ in Xia's 2023 study:
  Xia Y, Xu Y, Shi M, Liu S, Liu S, Wang H, Dai C, Ye Y, Liu M, Shang L, Wang Y, Wang P - "Effects of high-water fluoride exposure on IQ levels in school-age children: a cross-sectional study in Jiangsu, China" Expo Health 16:885-895 (2024). doi:10.1007/s12403-023-00597-2.
  https://link.springer.com/article/10.10 ... 23-00597-2
  In that study, no mention is made of the high iodine intake.

Introduction

With advancements in detection equipment and an increase in the frequency of examinations, thyroid nodules and goiter in children have garnered attention.

Objective

This study aims to determine the effects of high iodine and fluoride exposure on thyroid nodules and goiter in school-aged children.

Methods

We recruited children aged 8 to 12 from rural Jiangsu, China, based on the concentrations of iodine and fluoride in local drinking water and urine. Participants were divided into four groups: a group with high fluoride and iodine (HFHI), a group with high fluoride (HF), a group with high iodine (HI), and a control group (CONTROL). Fluoride levels in both drinking water and urine samples were measured using the ion-selective electrode method. Urinary iodine (UI) was assessed using inductively coupled plasma mass spectrometry, and children's thyroids were examined with portable ultrasound equipment equipped with a linear 7.5-MHz probe.

Results

The detection rates of thyroid nodules in the HFHI, HF, HI, and CONTROL groups were 10.4 %, 6.5 %, 7.7 %, and 2.8 %, respectively. The goiter detection rates were 3.8 %, 2.9 %, 3.8 %, and 1.1 %, respectively. In the HFHI group, statistically significant correlations were found between urinary fluoride (UF) and thyroid nodules (P = 0.011, adjusted OR and 95 % CIs were 2.29 [1.21, 4.32]), as well as between UI and thyroid nodules (P = 0.038, adjusted OR and 95 % CIs were 1.58 [1.04, 2.40]), and between UI and goiter (P = 0.014, adjusted OR and 95 % CI were 2.31 [1.19, 4.48]). In the HI group, there was a statistically significant link between UI and goiter (P = 0.005, adjusted OR and 95 % CI were 2.45 [1.31, 4.58]).

Conclusions

Combined high iodine and fluoride exposure may have an adverse effect on thyroid nodules in school-age children.

[admin]

Numerous concerns:

1.What were the actual towns?

Text states:

"In a certain town, the median urinary fluoride level exceeded 1.4 mg/L, while the median urinary iodine level was above 300 μg/L (HFHI group). In two other towns, only the median urinary fluoride level surpassed 1.4 mg/L (HF group), whereas in another town, only the median urinary iodine level was above 300 μg/L (HI group). In the final town, both fluoride and iodine levels were within normal ranges (CONTROL group)."

2. Urine Samples

Urine samples were not standardized. Spot samples were used which are highly inaccurate.

Fluoride urine samples were adjusted to specific gravity. Iodine samples were not. (It is well established that about fourteen repeated samples may be needed to estimate an individual's iodine intake.)

UIC levels were not categorized as per WHO guidelines. The "normal" category for UIC (100 - 300 μg/L) included the "more-than-adequate" category (200-300 μg/L). The "Control" group already had a median UIC of 240 μg/L [54, 652] --> certainly in the "more-than-adequate" category.

Control group also had a UF of 1.03 mg/L [0.34, 4.54] - also most certainly representing a high fluoride intake.