The following is a summary of “Impaired Sensitivity to Thyroid Hormones Is Associated With Decreased Vitamin D Levels in the Euthyroid Population,” published in the March 2024 issue of Endocrinology by Li, et al.
For a study, researchers sought to investigate the relationship between vitamin D levels and thyroid hormone sensitivity among euthyroid individuals.
The study included 6,452 euthyroid participants, and clinical parameters such as TSH, free thyroxine, 25-hydroxyvitamin D [25(OH)D], and other relevant indicators were extracted from the National Health and Nutrition Examination Survey 2007-2012. Thyroid hormone sensitivity was quantified using the Thyroid Feedback Quantile-based Index (TFQI), the TSH index (TSHI), and the thyrotropin thyroxine resistance index (TT4RI).
Individuals with impaired thyroid hormone sensitivity exhibited decreased 25(OH)D levels (TFQI, TT4RI: P < 0.05; TSHI: P = .05574) after adjusting for confounding variables. Age-specific analysis revealed negative correlations between thyroid hormone sensitivity indices and 25(OH)D within the 20 to 60 years subgroup, transitioning to positive correlations in the 60 to 80 years subgroup. Among females, thyroid hormone sensitivity indices and vitamin D levels were negatively associated, while among males, the relationships shifted from negative to positive when 25(OH)D levels exceeded 63.5 nmol/L, 56.7 nmol/L, and 56.7 nmol/L for TFQI, TT4RI, and TSHI, respectively. Stratification by race showed U-shaped curvilinear patterns similar to those observed in males. Subanalysis by body mass index (BMI) demonstrated varying associations between vitamin D and thyroid hormone sensitivity indices, with negative associations in the <25 kg/m2 and ≥30 kg/m2 subgroups and U-shaped associations in the 25-30 kg/m2 subgroup.
Impaired thyroid hormone sensitivity is correlated with decreased vitamin D levels among euthyroid subjects, with associations that vary by age, sex, race, and BMI. The findings underscored the complex interplay between vitamin D and thyroid function, highlighting the importance of considering multiple demographic factors in assessing their relationship.
Reference: academic.oup.com/jcem/article-abstract/109/3/691/7310986