Phthalate exposure and semen quality in infertile male population from Tianjin, China: Associations and potential mediation by reproductive hormones
Global decline in male fertility and their associations with ubiquitous exposure of phthalates (PAEs) have raised public concerns. However, the current epidemiological data are limited and controversial. Hence, we investigated possible associations between PAE exposure and male infertility. Eleven phthalate metabolites (mPAEs) were determined in urine and serum samples collected from eighty-eight males diagnosed with infertility from Tianjin, China. The median serum levels of mPAE were n.d. -3.63 ng/mL, which were 1-2 orders of magnitude lower than the urinary levels of n.d. -192 ng/mL. Negative associations were identified between urinary follicle-stimulating hormone (FSH) and MiBP and serum MCMHP, as well as testosterone (T) and luteinizing hormone (LH) and the molar concentrations of ∑mPAE, while positive association was found between T and the serum molar concentrations of ∑mDEHP. Positive associations were found between the molar concentrations of serum ∑mPAE and sperm concentration, sperm motility rate, and progressive motility, between mono (2-ethyl-5-carboxypentyl) phthalate (MECPP) and semen volume and total sperm number, and between MCMHP and progressive motility, while negative association was found between mono(2-ethyl-5-oxohexyl) phthalate (MEOHP) and progressive motility. Moreover, FSH was found to mediate the association between serum concentrations of MCMHP and progressive motility (mediation ratio = 41.6%), and LH to mediate the associations between serum concentrations of ∑mPAE and sperm concentration (mediation ratio = 45.7%) and sperm motility rate (mediation ratio = 29.0%). These results also suggested that serum levels of mPAE are a good predictor for male infertility. Further efforts need to be made on toxicological studies to systematically elaborate the internal mechanisms.