## 4 Discussion
[35] showed a significant decrease in TSH concentration in the blood of students who used mobile phones intensively (field frequency, 900 MHz). It appears that EMF may affect the pituitary gland by reducing the secretion of TSH, which is a typical response to various types of stress factors [36]. A significantly reduced amount of TSH may indicate hyperhyroidism. Hyperhyroidism as a result of EMF at 900 MHz frequency is suggested by the results obtained by [PERSON] et al. [37], who showed a significant increase in T3 and T4 concentrations in chicken embryos exposed to electromagnetic field. Notably, the results of the present study suggest that discontinuing EMF emission can normalize endocrine activity in the pituitary gland in terms of TSH secretion. It cannot be ruled out that the decrease in TSH secreted by the pituitary gland found in the current study may have resulted in secondary hypothyroidism and consequently led to a decrease in the rate of metabolic changes. However, verifying this conclusion would require additional determinations, i.e., the T3 and T4 concentrations, which may be good indications for further research. The safety of human exposure to an ever-increasing number and diversity of EMF sources, both at work and at home, has become a public health issue. To date, many in vivo and in vitro studies have revealed that EMF exposure can alter cellular homeostasis, endocrine function, and reproductive function. Reproductive disorders that may be associated with EMF exposure include male germ cell death, changes in the estrous cycle, alterations in reproductive hormones, variations in reproductive organ weights, reduced sperm motility, impaired early embryonic development, and decreased pregnancy success [38]. In our experiment, a statistically significant reduction in sperm motility was observed in the experimental group compared with the control group after 12 weeks of exposure and 4 weeks after the end of emission. These results may indicate the chronic impact of electromagnetic field on the tested parameter. In a study of rats exposed to EMF (900 MHz for 28 days), [PERSON] et al. [39] observed statistically significantly lower sperm motility in specimens subjected to EMF exposure. In addition, [PERSON] et al. [40] observed a significant reduction in sperm motility in rats exposed to 1800 MHz field emission for 5 weeks. [PERSON] et al. [41] also noted that radiofrequency electromagnetic field reduces sperm motility in rats. [PERSON] et al. [42] showed significantly lower sperm motility in rats exposed to 50 Hz EMF for 85 days. Moreover, other studies have shown that sperm motility in rats decreases with increasing magnetic field intensity [43]. Our study showed a statistically significant reduction in sperm viability in the group subjected to 12 weeks of EMF emission which persisted for 4 weeks after the end of emission. Furthermore, [PERSON] et al. [41] showed that radiofrequency electromagnetic fields significantly reduced the viability of rat sperm. During the experiment, sperm motility and viability decreased both during EMF propagation and four weeks after emission stopped. This is likely related to the fact that spermatogenesis in rats lasts about 50 days, meaning that male reproductive cells were exposed to EMFs throughout their development [44]. It seems that the decline in sperm quality is associated with oxidative stress caused by increased levels of free radicals. Reduced sperm motility and viability have been observed at high superoxide anion concentrations [45]. Free radicals oxidize membrane phospholipids, decreasing cell membrane fluidity, which is associated with impaired motility and reduced sperm viability [46]. The current study showed that this experimental factor had no statistically significant effect on the percentage of morphologically abnormal sperm in the experimental group rats compared with the control group rats. Similar results were obtained by [PERSON] et al.