Cross-sectional study finds fat-soluble vitamins A and D correlate with thyroid biomarkers in preconception women, indicating body mass index modifies thyroid autoimmunity risk.
Key Points
To investigate individual and combined associations of preconception fat-soluble vitamins with thyroid function and autoimmunity biomarkers, while assessing whether body mass index modifies these relationships.
Analyzed cross-sectional data from 4,947 preconception women with normal thyroid-stimulating hormone (TSH) levels categorized into low-normal and high-normal (≥ 2.5 mIU/L) groups.
Employed generalized linear regression, restricted cubic splines (RCS), and Bayesian kernel machine regression (BKMR) models to examine vitamin-thyroid relationships and BMI interactions.
Deficiency or severe deficiency in 25-hydroxyvitamin D was present in 87.5% of women, whereas sufficient levels were observed for vitamin A (80.9%), vitamin E (94.5%), and vitamin K (94.6%).
Vitamin A showed positive linear associations with high-normal TSH status (OR = 1.36, 95% CI: 1.04 to 1.77) and overall TSH levels (β = 0.10, 95% CI: 0.04 to 0.16; P for overall < 0.05, P for nonlinear > 0.05).
Multi-vitamin modeling identified a linear inverse association between 25-hydroxyvitamin D and thyroid peroxidase antibody positivity that was notably stronger in women with overweight or obesity.