A STUDY ON THE RELATIONSHIPS BETWEEN TRACE ELEMENTS AND SPERM QUALITY

Abstract

During the past 50 years, human sperm quality was observed to decrease, though sexual transmitted disease, one of the main causes of male infertility, decreased at the same time. Environmental factors, therefore, were obviously suspected. the adverse effects of some heavy metals (such as lead, cadmium and mercury) on male reproduction have been observed in experimental animals and occupationally exposed workers. However, few studies have been carried out to examine the relationships between human sperm quality and the concentrations of heavy metals of non-exposed persons. On the other hand, some essential trace elements have been believed to play important roles on male reproduction. The objectives of this cross-sectional study was: (1) To study the relationships between trace elements in blood and seminal plasma; (2) To establish the correlation between sperm quality and trace elements in blood and seminal plasma in non-exposed population. The 222 study subjects came from Singapore General Hospital who were undergoing initial screening for infertility in the Andrology Clinic. The semen screening included semen volume, sperm density, sperm motility and sperm morphology. The concentrations of cadmium, copper, lead, mercury, selenium and zinc in blood and seminal plasma ( except mercury in seminal plasma) were measured. In blood, significant positive associations were found between zinc and copper, selenium and mercury, and selenium and cadmium, while significant inverse correlations were observed between zinc and cadmium, and lead and mercury. In seminal plasma, however, positive associations were shown between cadmium, copper, selenium and zinc. In contrast, no element was found to correlate with lead. Interestingly, significant positive correlations were found for the three essential trace elements (copper, selenium and zinc) between blood and seminal plasma. No such relationship was noted for the toxic heavy metals (cadmium and lead). A significant inverse correlation was observed between the concentration of cadmium and sperm density (r=-0.15, p< 0.05) but not in normospermic men. After adjusting for confounding factors, such as age, cigarette smoking, alcohol drinking and the other elements, significant inverse correlations were observed between the concentration of cadmium in blood and sperm density (p < 0.05) and sperm motility (p < 0.05). In addition, this study also noted cigarette smoking may contribute to high concentration of cadmium in blood as well as lower sperm density. Cadmium in seminal plasma was also associated with low semen volume (r=-0.29, p<0.05). These findings suggest that subjects with low sperm density may be more vulnerable to cadmium than normospermic men. On the contrary, sinificant positive correlations were found between sperm density and the concentrations of selenium and zinc in seminal plasma in normospermic men but not in oligozoospermic men. After adjusting for confounding factors, such as age, cigarette smoking, alcohol intake and the other elements, significant positive correlation was observed between sperm density and the concentration of zinc in seminal plasma but not selenium level in seminal plasma.