This study showed that serum concentrations of LH were inversely associated with sperm motility and normal morphology, after adjusting for various lifestyle factors and other sex hormone levels. In addition, higher levels of FSH showed an independent association with a lower proportion of normal sperm morphology. No statistically significant association was observed between sex hormones and total sperm count or sperm concentrations. Our findings suggested that LH might play a central role in the sperm motility and morphology, supporting the utility of circulating LH levels as a biomarker for assessing sperm quality.
A few studies have investigated the relationship between circulating sex hormones and sperm parameters. Kumanov et al. found that serum concentrations of LH and FSH were inversely correlated with sperm count, motility, and morphology, while testosterone was not correlated [10]. Similarly, another study by Meeker et al. reported significant negative correlations of LH and FSH with sperm concentration, motility, and morphology; however, testosterone levels were significantly positively correlated with motility [11]. In contrast, two small studies reported that only FSH levels had a negative correlation with semen parameters, while LH and testosterone levels did not [7, 8]. Compared with those studies, the current study had relatively large sample size, included various sex hormones, adjusted for lifestyle factors, and performed mutual adjustment analysis. We found that LH, FSH, and TT were all inversely associated with sperm total motility; however, only LH had an independent association after adjusting for FSH and TT, supporting the central role of LH in sperm motility. Consistently, only LH levels was found to be inversely associated with sperm progressive motility. We also observed that LH and FSH were inversely associated with sperm morphology after mutual adjustment, suggesting that both of them are important for sperm to maintain normal morphology. To our knowledge, the current study represents a first attempt to disentangle independent effects of various sex hormones on sperm quality.
The primary role of LH in the male is to stimulate the production of testosterone by the Leydig cells which then, together with FSH, control spermatogonial cell formation and spermatogenesis in the Sertoli cells [17]. Early studies indicated that gonadal failure, a cause of infertility, was characterized by increased levels of LH and FSH [18]. Male patients with idiopathic oligozoospermia were also found to have a higher mean LH pulse frequency than the controls [19]. The increase in LH or FSH concentrations may reflect that the testicles have insufficient capacity for normal spermatogenesis. In the current study, we observed a suggestive association between LH/FSH and sperm concentration, although not statistically significant. On the other hand, LH may affect fructose utilization, glucose oxidation, and adenyl cyclase activity in sperm, which are important means by which spermatozoa derive energy for motility [20]. The acquisition of sperm motility occurs during sperm maturation in the epididymis, and LH receptors have been detected in epididymal epithelium [21, 22]. Moreover, in the absence of LH, addition of T and FSH can only partly rescue the phenotype of abnormal sperm [23]. These evidences are in support of our findings, suggesting a critical role of LH in sperm motility. Although recent studies support that LH may be also implicated in sperm morphology [24, 25], specific mechanisms remain unknown. More functional research is warranted to clarify the current results.
This study has several strengths, including relatively large sample size, inclusion of various sex hormones, adjustment for potential confounding, and mutual adjustment analysis to determine independent effects; however, our analysis was cross-sectional, which limited the ability to make causal inference. Additionally, only a single measurement of circulating hormones was available that may not represent long-term levels. Therefore, prospective studies with repeated assessment of circulating hormones are necessary to validate our findings.