Background Although sex hormones play critical roles in spermatogenesis and sperm maturation, it remains inconclusive whether circulating sex hormones can serve as non-invasive biomarkers to improve the assessment of sperm quality. Methods We systematically evaluated the association of various sex hormones in serum with sperm quality among 338 men in subfertile couples. Concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH), total testosterone (TT), total estradiol (E2),

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... and sex hormone-binding globulin (SHBG) were detected by chemiluminescent immunoassay. Free testosterone and estradiol were calculated using a validated algorithm. A generalized liner regression model controlling for lifestyle factors was used to evaluate the associations with sperm count, concentration, motility, and morphology.Results After adjusting for age, body mass index, current smoking and alcohol drinking, LH, FSH, and TT levels were all inversely associated with sperm motility (all P for trend < 0.05); however, in mutual adjustment analysis, only LH remained an inverse association with sperm motility after adjusting for FSH and TT levels (P for trend = 0.04). Higher concentrations of LH were also associated with lower sperm progressive motility (P for trend = 0.04). Moreover, LH and FSH levels were both inversely associated with normal sperm morphology (P for trend = 0.04 and 0.02, respectively). Conclusions Increased levels of LH are associated with poor sperm motility and morphology, suggesting that LH may play a central role in sperm maturation. Future studies are warranted to assess potential clinical utility of LH for risk stratification and tailed prevention of male infertility.