Concentração de zinco e câncer de tireoide: um estudo de revisão e metanálise

Abstract

Thyroid cancer (TC) represents the most common group of endocrine tumors and its incidence has increased rapidly over the last four decades. Investigations related to trace element imbalance have gained relevance, since the thyroid gland is sensitive to these elements. Studies reveal that some trace elements play a fundamental role in several physiological processes, while reduced levels of essential trace elements may be associated with carcinogenic evolution. In this context, zinc (Zn) emerges as an essential element for the action of the thyroid hormone, and possibly related to the pathogenesis of TC. This dissertation aims to contribute to the discussion on the association between low serum Zn concentrations and the occurrence of TC, through a systematic review and meta-analysis of the most recent scientific evidence. The search was carried out in the PubMed/MEDLINE, Scopus, Embase, LILACS and Web of Science databases, looking for observational studies that investigated changes in serum Zn concentration and the occurrence of TC in adults, published until december 2024. No restrictions were imposed on language or publication period. The primary outcome was low serum Zn concentration and the occurrence of TC. Three independent reviewers selected the studies and extracted the data from the original publications. The risk of bias was assessed using the Newcastle-Ottawa Quality Assessment Scale. Data analysis was performed using R software (V.4.3.1), and heterogeneity was calculated using the I² statistic, with results based on random effects models. A total of 10 studies (n = 7 case-control and n = 3 cross-sectional) with sample sizes ranging from 44 to 294 individuals were included. The results indicated that serum Zn levels were not significantly lower in patients with TC compared with healthy controls (mean difference: -251.77; 95% confidence interval: -699.09, 195.54; I² = 100%, very low certainty). To elucidate the role of serum Zn in the occurrence of TC, further investigations, including rigorously designed observational studies with representative samples and improved control of potential confounding variables are indispensable.