Thyroid function, intelligence, and low-moderate fluoride exposure among Chinese school-age children

Area of Science:

• Environmental Health
• Pediatric Endocrinology
• Neurodevelopmental Toxicology

Background:

• Thyroid hormones (THs) are essential for normal brain development.
• The effects of low-to-moderate fluoride exposure on thyroid function and children's intelligence are not well understood.

Purpose of the Study:

• To investigate the association between low-to-moderate fluoride exposure and thyroid function in children.
• To examine how fluoride exposure and thyroid function relate to children's intelligence (IQ scores).

Main Methods:

• A cross-sectional study of 571 children (aged 7-13 years) in Tianjin, China.
• Measurement of fluoride in drinking water and urine.
• Assessment of thyroid function via serum total triiodothyronine (TT3), total thyroxine (TT4), free triiodothyronine (FT3), free thyroxine (FT4), and thyroid-stimulating hormone (TSH).
• Statistical analysis using multivariable regression models.

Main Results:

• Increased fluoride exposure (water and urine) was associated with elevated TSH levels.
• Higher fluoride exposure correlated with decreased TT4 and FT4 levels.
• Fluoride exposure showed an inverse relationship with IQ scores.
• Elevated TT3 and FT3 levels were linked to higher intelligence, with TSH significantly modifying the fluoride-IQ association.

Conclusions:

• Low-to-moderate fluoride exposure is linked to changes in childhood thyroid function.
• These thyroid alterations may influence the relationship between fluoride exposure and children's intelligence.