Urinary trace elements and thyroid nodule formation in a longitudinal cohort of older women: Findings from KoGES

Thyroid nodules are common in older populations, but the role of trace elements in their development and growth remains unclear. Previous studies have reported inconsistent findings regarding the association between trace elements and thyroid nodules. This study investigated the associations between urinary concentrations of various trace elements and the prevalence and incidence of thyroid nodules in older women, a population at higher risk for thyroid disorders. Cross-sectional and longitudinal analyses were conducted using data from 653 women aged 60 years and older in the Ansung cohort of the Korean Genome and Epidemiology Study (KoGES). Urinary concentrations of 18 elements were analyzed using inductively coupled plasma mass spectrometry (ICP-MS), and mercury was analyzed using a Direct Mercury Analyzer (DMA). Logistic regression was used to assess associations between trace element exposure and thyroid nodule prevalence, stratified by nodule size (3.0-4.9 mm, 5.0-9.9 mm, and ≥10.0 mm). Higher urinary concentrations of Mn (OR 2.04; 95 % CI, 1.27-3.28), Cu (OR 1.71; 95 % CI, 1.08-2.72), and Co (OR 1.48; 95 % CI, 0.94-2.31) were significantly associated with larger thyroid nodules (≥10.0 mm). Zinc (OR 1.33; 95 % CI, 0.84-2.11) showed a weaker but positive association with larger nodules, while uranium exposure was notably linked to the development of new nodules during follow-up (OR 7.70; 95 % CI, 1.56-38.10 for nodules ≥5.0 mm). The findings suggest that trace elements, particularly Mn, Cu, Co, Zn, and U, may contribute to the formation and growth of thyroid nodules in older women. Future research should investigate the underlying mechanisms and expand to other populations to better understand these associations.