THYROID cancer incidence has risen steadily in recent decades, prompting ongoing investigation into modifiable risk factors. Among these, vitamin D has attracted considerable interest due to its role in cell growth regulation and immune function. While many observational studies have examined a potential link between vitamin D levels and thyroid cancer risk, results have remained inconclusive. A recent meta-analysis brings new clarity to the association. Notably, the analysis found that people with thyroid cancer had significantly lower serum vitamin D levels than healthy controls.
Researchers conducted a systematic review and meta-analysis of 23 studies that compared vitamin D levels in thyroid cancer patients and matched control groups. Major scientific databases including Embase, Web of Science, and PubMed were searched to identify relevant human studies. The team applied a random-effects model to calculate the standardised mean difference (SMD) in vitamin D levels, as well as the odds ratio (OR) for vitamin D deficiency. Subgroup and meta-regression analyses were performed to investigate sources of heterogeneity, considering factors such as seasonality, measurement timing, and study type. A p-value below 0.05 was considered statistically significant.
The pooled results showed that individuals with thyroid cancer had significantly lower vitamin D levels than those without (SMD: -0.38; 95% CI: -0.62–-0.14). Furthermore, thyroid cancer patients were more likely to be vitamin D deficient compared to controls (OR: 1.33; 95% CI: 1.02–1.73; p<0.05). Subgroup analyses largely supported these findings across multiple study characteristics, with the exception of post-operative vitamin D measurements.
This meta-analysis reinforces a significant association between low serum vitamin D levels and increased thyroid cancer risk. While causality cannot be inferred, the findings suggest clinicians may wish to consider vitamin D status when assessing thyroid cancer risk profiles. Importantly, the study highlights several limitations, including heterogeneity in sampling methods and timing, and variability in control groups. Standardised, prospective research is needed to establish the role of vitamin D in thyroid cancer prevention or management, and to determine whether supplementation could be clinically beneficial.
Reference
Yang L et al. Association between vitamin D serum levels and thyroid cancer: a meta-analysis. Front Endocrinol (Lausanne). 2025;16:1602844.
