To obtain an accurate characterization of a male fertility status, semen analysis is a well established procedure. The basic semen analysis measures sperm concentration, sperm motility, and sperm morphology. To elucidate semen abnormalities, further evaluation is necessary to interpret the defect. Several environmental and endocrine factors may cause male infertility. The goal of the study is to evaluate the level of lead in the seminal plasma in male partners of infertile couples undergoing infertility evaluation, and to observe the association among sperm quality, pregnancy rate and lead concentration in the semen. The major finding in the study is that lead concentration in the seminal plasma contributes to the poor sperm count in the patients undergoing infertility evaluation and treatment. The patients in this study had no histories of lead poisoning or occupational exposure to lead. This indicates that chronic systemic low-level exposure to environmental toxicants such as lead may damage the reproductive function in general population. To our knowledge, this is the first study to show that low level of lead accumulation in seminal plasma may affect sperm amount for men without occupational exposure to lead. Exposure to environmental toxicants may result in poor-quality gametes and aneuploidy in gametes [14, 15]. Some studies demonstrated that lead may lessen normal sperm metabolism through suppressing the sperm creatine kinase, contributing to infertility in men . The relationship between such exposures and poor-quality gametes needs to be addressed in future study.
The previous studies demonstrated that the infertile couples without occupational exposure to lead exhibited high blood lead concentrations, attributable to poor IVF outcome related to poor oocyte quality and altered sperm function [17–19]. Some studies indicated that effects of smoking on blood lead levels in workers may affect semen quality . However, the mechanisms of the actions underlying its toxic effects on male reproductive ability remain controversial. The gonadotropins bind specific receptors on the reproductive cell surface to stimulate gonadal steroidogenesis and gametegenesis. Since these receptors for gonadotropins are localized on the surface of the cell membrane, membrane integrity is important for gonadotropic binding, steroidogenesis, and gamete growth. The lead concentration in the tissue could affect hormone receptor kinetics, enzyme activities and hormone secretion . Although environmental exposure to lead may impair spermatogenesis, as shown in several animal studies [3, 21], similar data in human are generally limited. The above-mentioned data demonstrate that heavy metals intoxication alters steroidgenesis and gamete growth. Environmental low-level exposure to lead is a rising health issue, and more studies are encouraged to elucidate the lowest adverse effects of lead concentrations in biological fluids and tissue levels. The threshold level has been difficult to establish due to the selection of the exposure indicator and the reproductive endpoints . Lead can be measured in reproductive organs, including prostate and seminal vesicles. Lead appears to accumulate in the epididymis, however, the distribution of lead in male reproductive tracts has not been well established. The association observed in our study between lead in semen compartments and sperm count is significant. The association between lead concentration in semen and sperm count may result from lead-detrimental spermatogenesis rather than lead-altered hypothalamic-pituitary-gonadal function . Further studies are required to verify the impact of lead on semen environment and spermatogenesis.
Although blood lead level reflects recent exposure to lead, it is unclear whether the adverse health effects of lead that are observed are related to current or cumulative exposures. The previous studies indicate that workers exposed to lead had lower sperm count and higher teratozospermia count [24, 25]. An negative correlation between blood lead concentrations and poor semen quality has been shown . However, no association was observed between seminal plasma lead concentrations and semen quality in some studies [8, 26]. The possible factors for the drawbacks are limited detecting methods and less sensitive examinations of environmental effects in seminal plasma lead concentrations. The results of the current study draw a more definite conclusion on the relationship between seminal plasma lead concentrations and sperm count in men without occupational exposure to lead.