The association between the serum essential
metal elements (
magnesium,
iron,
copper,
zinc, and
calcium) and
thyroid nodules is still inconsistent. The current study aims to investigate the relationship of
metal elements with
thyroid nodules and their malignant tendency. A total of 6480 Chinese euthyroid adults were included in our study. We collect basic information through questionnaires and medical checkups. We diagnose
thyroid nodules by ultrasound and detect serum trace
metal concentrations by using an automatic biochemical analyzer. Binary and multinomial logistic regressions were used to investigate the associations. As a result, we found that serum
copper concentrations were positively associated with
thyroid nodules in the second, third, and fourth quartiles, compared to the first quartile (P = 0.024, P = 0.016, P = 0.032) in women and P for trend is 0.038. There is a significant sex-specific association between
copper concentrations and
thyroid nodules (P for interaction = 0.009). The results of the multinomial logistic regression analyses indicate high serum
calcium and
magnesium concentrations emerged as consistent risk factors for
thyroid nodules in both genders, whereas low
zinc was a sex-specific factor. We also observed significant sex interactions in the relationships of
magnesium (P for interaction = 0.043) with
thyroid nodules with malignant tendency among participants with
thyroid nodules. In conclusion, our study suggests that gender is an important factor when studying the association between serum metals and
thyroid nodules. The imbalance of selected
metal elements (
calcium,
copper,
zinc, and
magnesium) may relate to
thyroid nodules and their malignant tendency, and future prospective studies are needed to further confirm the associations.