Serum calcium improves the relationship between fluoride exposure and hypothalamic-pituitary-testicular axis hormones levels in males—a cross-sectional study on farmers in the lower reaches of the Yellow River

• Published in: Environmental pollution (1987) Vol. 363; no. Pt 1; p. 125084
• Main Authors: Wang, Guoqing, Duan, Leizhen, Du, Yuhui, Fu, Xiaoli, Liu, Bin, Zhang, Xuanyin, Yu, Fangfang, Zhou, Guoyu, Ba, Yue
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 15.12.2024
• Subjects: Adult; blood serum; calcium; Calcium - blood; China; Cross-Sectional Studies; Farmers - statistics & numerical data; Fluoride; fluorides; Fluorides - blood; Gonadotropin-Releasing Hormone; Humans; Hypothalamic-pituitary-testicular axis; Hypothalamo-Hypophyseal System - drug effects; Hypothalamo-Hypophyseal System - metabolism; Male; male reproductive system; males; Middle Aged; Modification; Occupational Exposure - statistics & numerical data; pollution; regression analysis; Rivers - chemistry; Serum calcium; Sex Hormone-Binding Globulin - analysis; Sex Hormone-Binding Globulin - metabolism; Testis - drug effects; Testosterone - blood; toxicity; Yellow River; China; Yellow River; Modification; CG; CI; Hypothalamic-pituitary-testicular axis; HFG; TSI; FEI; HPT; E2; HCG; SC; MCG; UF; LCG; Fluoride; T; Serum calcium; FSH; FTI; GnRH; LH; SHBG; BMI
• ISSN: 0269-7491; 1873-6424; 1873-6424
• DOI: 10.1016/j.envpol.2024.125084

Numerous studies have reported the toxicity of fluoride to the male reproductive system, but epidemiological evidence is limited. We conducted a cross-sectional study in Kaifeng City, Henan Province in 2011 to explore the association between fluoride exposure and hypothalamic-pituitary-testicular (HPT) axis hormones in men. Morning urinary fluoride (UF), serum HPT axis hormones and serum calcium (SC) concentrations were detected. Percent changes and 95% confidence intervals in HPT axis hormones associated with UF were estimated using adjusted linear regression models, and performed subgroup analysis based on SC levels. The restricted cubic spline model was used to fit nonlinear relationships. For every 10% increase in UF, the concentrations of serum GnRH, T, SHBG and TSI decreased by 2.13%, 2.39%, 2.19% and 1.96%, while E2 and FEI increased by 1.11% and 3.33%. Subgroup analysis showed that for every 10% increase in UF, the levels of GnRH, T, TSI and FTI decreased by approximately 3.15%, 5.49%, 4.47% and 5.14%, while the E2 level increased by 2.92% in low-serum-calcium group (LCG). The levels of GnRH and T decreased by approximately 2.97% and 1.82% in medium-serum-calcium group (MCG). In high-serum-calcium group (HCG), serum SHBG levels decreased by 4.70%, while FTI and FEI levels increased by 4.93% and 4.20% as UF concentration increased (P < 0.05, respectively). The non-linear relationship between serum GnRH and UF concentrations presented an approximately inverted U-shaped curve, with a turning point UF concentration of 1.164 mg/L (P < 0.001), and their nonlinear relationship in LCG and MCG were similar to that in the overall subjects. In conclusion, excessive exposure to fluoride can interfere with male serum HPT axis hormones, and a moderate increase in SC alleviates the effect of fluoride. Prospective cohort studies are essential to confirm the causality. [Display omitted] •Fluoride exposure could interfere with HPT axis hormones levels in adult males.•An inverted U-shaped association between serum GnRH and UF levels was observed.•Serum calcium attenuated the interference of fluoride exposure on HPT axis hormones.