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

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. (C) 2008 Elsevier Inc. All rights reserved.