Circulating estradiol in men is inversely related to urinary metabolites of nonpersistent insecticides

Abstract

Background: Estradiol plays an important role in male reproductive health as a germ cell survival factor. Chlorpyrifos and carbaryl, nonpersistent insecticides to which the general population are commonly exposed, were recently shown to inhibit estradiol metabolism in vitro which could lead to altered hormone balance.

Methods: Subjects (N=322) were the male partners in couples presenting to a Massachusetts infertility clinic from years 2000-2003. 3,5,6-Trichloro-2-pyridinol (TCPY), the major urinary metabolite of chlorpyrifos and chlorpyrifos-methyl, and 1- and 2-naphthol (1N and 2N), urinary metabolites of carbaryl and naphthalene, were measured in a spot urine sample from each subject. Estradiol, sex hormone binding globulin (SHBG), and prolactin were measured in serum collected from subjects during the same clinic visit.

Results: Using multiple linear regression, an interquartile range (IQR) increase in TCPY was associated with a 1.36 pg/mL decline (95% confidence interval=-2.91 to -0.22) in estradiol concentration. When estradiol and TCPY were divided into quintiles, there was a dose-dependent increase in the odds of being in the lowest estradiol quintile with increasing TCPY quintiles.

Conclusion: On a population level, these reductions in estradiol levels are of potential public health importance because of widespread exposure to TCPY and its parent insecticides.

Figures

Figure 1

Adjusteda regression coefficients for a change in estradiol level associated with increasing quintiles of SG-adjusted TCPY (N=322). P-value for trend = 0.03. aAdjusted for ln-transformed SHBG, age, BMI, and season.

Figure 2

Adjusteda regression coefficients for a change in estradiol level associated with increasing quintiles of SG-adjusted 1-naphthol (N=322). P-value for trend = 0.09. aAdjusted for ln-transformed SHBG, age, BMI, and season.

Figure 3

Adjusteda regression coefficients for a change in ln-adjusted prolactin level associated with increasing quintiles of SG-adjusted TCPY (N=322). P-value for trend = 0.01. aAdjusted for age and time of day blood sample was collected.

Figure 4

Adjusteda odds ratios for having estradiol level in the lowest quintile (< 25 pg/mL) with increasing SG-adjusted TCPY quintiles (N = 322). P-value for trend = 0.002. aAdjusted for age and time of day blood sample was collected.