The Association Between Environmental Cadmium Exposure and Parathyroid Hormone Levels

Cadmium exposure is associated with renal dysfunction and bone damage. Chronic kidney disease and bone loss are also related to parathyroid hormone (PTH). However, whether cadmium exposure affect PTH level is not completely understood. In this study, we observed the association between environmental cadmium exposure and PTH levels in a Chinese population. A ChinaCd study was performed in China in 1990s which included 790 subjects living in heavily, moderately and low cadmium polluted area. 354 of them (121 men and 233 women) also had the data of serum PTH. The cadmium levels in blood (BCd) and urine (UCd) were determined by flame atomic absorption spectrometry. Serum PTH was detected by immunoradiometric assay. Renal function was assessed based on urinary N-acetyl-β-d-glucosaminidase (UNAG), β₂-microglobulin (UBMG) and urinary albumin (UALB). The median BCd and UCd levels were 4.69 μg/L and 5.50 μg/g creatinine. The BCd, UCd, UNAG, UBMG and UALB levels in subjects with low PTH (< 5.0 ng/L) were significantly higher than those with PTH ≥ 5.0 ng/L (p < 0.05 or p < 0.01). Spearman correlation analysis also showed that UCd level was negatively correlated to PTH levels (r = -0.17, p = 0.008) in women. A weak correlation was also observed between PTH level and BCd in women (r = -0.11, p = 0.09) and UBMG in total population (r = -0.114, p = 0.07). Univariable and mutivariable logistic regression analysis both demonstrated that high BCd (> 10 μg/L) (odds ratio (OR) = 2.26, 95% confidence interval (CI):1.10-4.63; OR = 2.36, 95%CI: 1.11-5.05) and UCd level (> 20 μg/g cr) (OR = 2.84, 95% CI:1.32-6.10; OR = 2.97, 95%CI: 1.25-7.05) were associated with high risk of low PTH. Our data showed that environmental cadmium exposure was associated with low PTH level.