Calcitropic hormones and occupational lead exposure

The authors sought to clarify in a cross-sectional study the possible associations between homeostatic regulators of calcium and occupational exposure to lead. Subjects were 146 industrial male employees, 56 with and 90 without occupational lead exposure. The main outcome measures were serum concentration of parathyroid hormone (PTH) and 1,25-dihydroxyvitamin D (calcitriol). The median values of blood lead were 40.5 μg/dl in the exposed group and 4.0 μg/dl in the controls. There were no differences between groups in dietary history and serum calcium levels. PTH and calcitriol levels were significantly higher in the exposed than in the nonexposed subjects (42.0 ± 24.2 vs. 33.6 ± 14.9 pg/ml, p <0.05; and 83.8 ± 27.0 vs. 67.9 ± 17.6 pmol/liter, p <0.001, respectively). Multivariate analyses showed that after controlling for possible confounders, occupational lead exposure (no/yes) was independently associated with PTH level (pg/ml) (β = 7.81, 95% confidence interval (Cl) 3.7-11.5) and with calcitriol (pmol/liter) (β = 12.3, 95% Cl 3.84-20.8). It is concluded that subjects occupationally exposed to lead show a substantial compensatory increase in PTH and calcitriol activities which keep serum calcium levels within normal range. This may be of clinical significance since a sustained increase in calcitropic hormones in susceptible subjects may eventually increase the risk of bone disorders.