Clinical Pharmacist and Master’s student in Clinical Pharmacy with research interests in pharmacovigilance, behavioral interventions in mental health, and AI applications in clinical decision support. Experience includes digital health research with Bloomsbury Health (London) and pharmacovigilance practice in patient support programs. Published work covers drug awareness among healthcare providers, postpartum depression management, and patient safety reporting. 
Clinical Pharmacist and Master’s student in Clinical Pharmacy with research interests in pharmacovigilance, behavioral interventions in mental health, and AI applications in clinical decision support. Experience includes digital health research with Bloomsbury Health (London) and pharmacovigilance practice in patient support programs. Published work covers drug awareness among healthcare providers, postpartum depression management, and patient safety reporting. What was reviewed?
This systematic review and meta-analysis, titled “Zinc Status and Occurrence of Thyroid Cancer,” critically examined published observational studies to determine whether a relationship exists between low serum zinc concentrations and the occurrence of thyroid cancer. The research was motivated by the rising incidence of thyroid cancer globally and the potential biological role of zinc, an essential trace element for thyroid hormone function and antioxidant defense. The primary outcome assessed was the difference in serum zinc levels between individuals with thyroid cancer and healthy controls. Measurement methods for zinc included atomic absorption spectrometry, inductively coupled plasma mass spectrometry, and related techniques, reflecting real-world laboratory variability. The review followed established methodological guidelines for systematic reviews and meta-analyses (MOOSE, PRISMA) and included a rigorous risk of bias assessment to ensure the trustworthiness of the findings.
Who was reviewed?
The review incorporated data from ten observational studies, including seven case–control and three cross-sectional studies, with sample sizes ranging from 44 to 294 participants. The studies collectively represented populations from Serbia, China, Pakistan, Turkey, Korea, Poland, Kuwait, Iran, and Africa, thus covering both Asian and non-Asian settings. Participants were adults and, in some studies, elderly individuals; two studies focused exclusively on women. Thyroid cancer types evaluated included papillary, follicular, medullary, anaplastic, and unspecified categories. Control groups comprised apparently healthy individuals without a history of thyroid cancer. Zinc status was assessed using serum, plasma, or whole blood samples, and measurement techniques varied between studies. The diversity of diagnostic methods and zinc assessment approaches reflected the heterogeneity typical of real-world clinical and laboratory settings, which is relevant for heavy metal certification programs seeking generalizable evidence.
Most important findings
| Critical Point | Details |
|---|---|
| No significant association between low serum zinc and thyroid cancer occurrence | The meta-analysis, synthesizing data from two compatible studies, found no statistically significant difference in serum zinc levels between thyroid cancer patients and controls (mean difference: –251.77; 95% CI: –699.09, 195.54). |
| High heterogeneity among included studies | The I² statistic was 100%, indicating substantial methodological and population heterogeneity, stemming from different sample types (serum, plasma, whole blood), diagnostic categories, measurement methods, and regional diversity. |
| Variable results in individual studies | While some studies (e.g., Stojsavljević et al.) found significantly lower zinc in cancer patients, most did not, and the overall evidence was inconsistent. Measurement techniques and zinc cut-off values varied widely across studies. |
| Measurement of zinc as a biomarker remains questionable | Evidence suggests that serum/plasma zinc is a useful population-level marker but may not reliably indicate individual deficiency, especially in cancer or inflammatory contexts due to redistribution and acute phase reactions. |
| Relevance of dietary and metabolic factors | Dietary zinc intake, absorption inhibitors (like phytates), and interactions with other metals (notably copper) may confound serum zinc status and its association with thyroid cancer, complicating certification thresholds for industry. |
| Need for more robust, standardized research | The review emphasizes the necessity for larger, well-designed studies with standardized zinc measurement methods, proper control of confounders, and stratification by cancer type and stage to draw definitive conclusions for certification. |
Key implications
For heavy metal certification programs, this review suggests that serum or plasma zinc levels alone are not reliable indicators for thyroid cancer risk assessment or certification, due to high variability and lack of consistent association. Standardized measurement and clear reference values are essential for any future regulatory use.
Citation
Soares AA, Nagashima YG, Piuvezam G, Alves CX, de Medeiros KS, Lopes MMGD, Brandao-Neto J. Zinc Status and Occurrence of Thyroid Cancer: Systematic Review and Meta-Analysis. Nutrients. 2025;17:2820. doi:10.3390/nu17172820
Heavy metals are high-density elements that accumulate in the body and environment, disrupting biological processes. Lead, cadmium, arsenic, mercury, nickel, tin, aluminum, and chromium are of greatest concern due to persistence, bioaccumulation, and health risks, making them central to the HMTC program’s safety standards.
