Pesticides, as endocrine disrupting chemicals, can also alter the reproduction function affecting hypothalamic and pituitary axis which may alter the secretion of GnRH, LH, and FSH widely by modifying the feedback of endogenous hormones. Several studies have demonstrated that low-dose of DDT and methoxychlor can result in a reduction of hypothalamic and pituitary functions (56, 57).

Several experimental studies on rats have reported that perinatal, juvenile, or adult exposure to EDCs, disrupt the hypothalamic control of pituitary gonadotropin synthesis leading to a disruption of gonadal steroid production and androgens cyclicity (58–62). These studies suggest that EDCs exposure affects the expression of GnRH and kisspeptin, influences the pulsatile launch of GnRH, and interferes with the regulation of gonadotropin production from the pituitary axis (63). These impacts can arise from periodic exposures during perinatal, juvenile increase, and adulthood at low concentrations and lead to disruption of steroidogenesis, estrous cyclicity and the onset of puberty (64).

Hyperthyroidism is characterized by increased total thyroxine (T4) levels which lead to an increase in sex hormone binding globulin (SHBG) in circulation and a decrease in the level of testosterone (65).

These environmental substances can disrupt exclusive tiers of the hypothalamic–pituitary axis, including the synthesis, metabolism, and organic effects of thyroid hormones. Given the significance of this gland for homeostasis, it is far crucial to better understand the mechanisms involved in the action of EDCs on thyroid function (66).

Several studies have shown that phthalates reduce testosterone production and testicular expression of genes and proteins involved in steroid synthesis, but few studies have described alterations in the expression of PPARs (peroxisome proliferator-activated receptors) in testes and other tissues. Phthalates and their metabolites have been extensively studied for their impact on sexual development and fertility because of their hormone-like effects (67). Several studies, focusing on the biochemical (enzymes implication) effects, have suggested their involvement in PPARs pathways, to have a better understanding of these physiological modifications. These compounds are known to activate these receptors, specifically PPARα and PPARγ, which are nuclear receptors involved in regulating various physiological processes, including lipid metabolism and inflammation (68, 69). By acting as agonists for PPARα and PPARγ, thus disrupting their normal function, these chemicals can lead to dysregulation of the hormonal balance and perturbations in endocrine signaling pathways (70). Consequently, this disruption can potentially affect the expression of aromatase (encoded by CYP19 gene), an enzyme crucial for estrogen synthesis, through conversion of androgens to estrogens in gonadal and extra-gonadal tissues. This enzyme can convert testosterone to estradiol (71). Dysregulation of aromatase can disturb the balance of sex hormones, contributing to reproductive issues and infertility. In fact, both deficiency and excess of aromatase may result in many disorders related to sex hormones profile (72). These findings highlight the complex mechanisms through which phthalates can impact sexual development and fertility, with PPARα and PPARγ pathways playing a pivotal role in these adverse effects.

In the context of male infertility, certain obesogenic EDCs like Bisphenol A (BPA) (73), Phthalates (74), Perfluoroalkyl Substances (PFAS) (75), Polychlorinated Biphenyls (PCBs) (76), Polybrominated diphenyl ethers (PBDEs) (77), and Atrazine (28) can impact male infertility and might be linked to reduced sperm quality, hormonal imbalances, and metabolic disruptions that contribute to obesity (78).

Numerous studies have been carried out in animal models to explore the impacts of various factors on physiological processes (Table 1). There are a few observational studies conducted in humans (Table 2). Animal studies provide valuable insights to better understand the implications of these factors in human health (89, 90).

Several animal experimental studies working on xenobiotics inducing a testicular disorder, reported that only some have caused reproductive damage in men. Pham and colleagues in 2019 exposed the pregnant mice and their offspring to different doses of glyphosate and a specific glyphosate based on herbicide (GBH). The doses tested were 0.5 mg/kg/day, 5 mg/kg/day and 50 mg/kg/day. The exposure began at embryonic day 10.5 (E10.5) and continued until 20 days postpartum. The male offspring of the treated mice were analyzed at different ages: 5 days old, 20 days old, 35 days old, and 8 months old. The study outcome showed that glyphosate exposure (but not GBH exposure) led to changes in the structure of the testes (testes morphology) in males that were 20 days old and resulted in decreased serum testosterone concentrations in males that were 35 days old. Additionally, they found that the spermatozoa number decreased by 89 and 84% in 0.5 and 5 mg/kg/day of GBH and glyphosate groups, respectively. This data suggests that, at low doses, glyphosate and GBH have endocrine disrupting effects on male reproduction (91).

Dysregulation of estrogen synthesis or estrogen receptor function in the efferent ducts results in testicular inflation and seminiferous tubular atrophy. Subsequently, testicular atrophy is provoked after chronic or sub chronic exposures to environmental toxicants, lesions in efferent ducts and head of the epididymis which can lead to permanent infertility (92).

Numerous studies showed that pesticide exposure damaged some testis functions (secretion of androgens in Leydig cells or Inhibin B in Sertoli cells). A study published in 2012 showed that Leydig cells are damaged after 1 to 48 h of exposure to glyphosate-based herbicide. Within 24-48 h, this toxic also damaged the other cells, mainly by necrosis, conversely to glyphosate alone which exerted a toxic effect on Sertoli cells. At long term exposition, it also induces apoptosis in germ cells and in Sertoli cells. At lower nontoxic concentrations of glyphosate (1 ppm), the main impact is a testosterone decrease by 35%. These results show that the pesticide has an endocrine impact at very low environmental doses (93). In addition to pesticides, scientific studies have shed light on how phthalates disrupt testosterone production in Leydig cells in the testes, impacting fetal sexual development. Detrimental effects of phthalate exposure on Steroidogenic Acute Regulatory (StAR) protein expression have been highlighted. In fact, phthalates interfere with Leydig cells by decreasing the production of StAR protein. This reduction in StAR protein levels hinders the transport of cholesterol into the mitochondria, a critical step in the synthesis of testosterone (94). This disruption in testosterone production during fetal development can have profound consequences on sexual differentiation and maturation, potentially leading to reproductive health issues later in life. The role of phthalates in fetal sexual development is a complex area of research, and recent studies continue to underscore the significance of understanding the mechanisms through which these chemicals impact endocrine function and reproductive outcomes.

A growing body of evidence suggests a correlation between exposure to Bisphenol A (BPA) and the progression of prostate cancer. The potential impact of BPA on the advancement of this malignancy raises concerns about its role in influencing disease development and severity (95). A Spanish study included 4,812 participants (547 breast cancer cases, 575 prostate cancer cases and 3,690 sub-cohort participants) and aimed to analyze serum BPA concentrations. The study outcome reported that elevated level of serum BPA is associated with 40% increase in risk of prostate cancer while no significant association have been found between BPA and breast cancer (96).

It’s well known that BPA exposure is associated with reproductive health disorders including cryptorchidism, a condition characterized by the incomplete descent of the testes into the scrotum (97). A prospective study was conducted on 98 children with congenital unilateral cryptorchidism and 19 healthy boys. The study findings suggest a significant increase in BPA level in the cryptorchid group 61.4% (98). Furthermore, Shi et al. reported that prenatal exposure of male mice to BPA leads to a decrease in sperm quality including sperm count and sperm motility. Additionally, BPA has been linked to a disturbance in the distribution of spermatogenesis stages (99). Regarding the pathogenesis impact of BPA, research has suggested that BPA has a positive association between pesticide levels and risk of hypospadias. A study including 668 mother–son pairs from Southern Spain indicated a significant negative impact between exposure to BPA and other phenols during pregnancy and male genital development including cryptorchidism and hypospadias (100, 101).

According to its estrogenic properties, BPA exposure during critical windows of fetal development could potentially disrupt the normal hormonal signaling pathways such as INSL3 (insulin-like 3) (87). This hormone is involved in the development of the male reproductive system especially in the release of testosterone and the descent of the testes into the scrotum before birth (102). A French case–control study has demonstrated the negative correlation between blood BPA levels and INSL3 levels leading to cryptorchidism. This study included a total of 52 cryptorchid (26 transient, 26 persistent) and 128 control boys from southern France. The study outcome revealed that chronic fetal exposure to BPA leads to the disturbance of INSL3 pathway (INSL3 reduction levels, p = 0.01; R² = 0.05) and the occurrence of cryptorchidism (87). Another experimental study published by Desalegn confirmed that perinatal exposure to EDCs is associated with increased congenital cryptorchidism (103). Anogenital distance (AGD) including anoscrotal distance (ASD) and anopenile distance (APD) in males can also be link to perinatal exposure to EDCs (88).

Evidence suggests that BPA could potentially impact estrogen and androgen receptors, and interfere with LH binding and testosterone synthesis in Leydig cells (104) (Figure 1).

Endoplasmic reticulum (ER) stress has been shown to contribute in defective spermatogenesis in both animal models and humans (105). Several studies have reported a significant increase in ROS in infertile men compared to fertile men (105, 106). Exposure to environmental toxins like BPA can induce ER stress and contribute to testicular cell damage leading to impaired spermatogenesis and apoptosis (107). Elevated level of ROS can trigger protein folding, Unfolded Protein Response (UPR) activation and affect stress transducers like GRP78, PERK and potential mitochondrial dysfunction (106). The intrinsic pathways of apoptosis including mitochondrial pathway and ER stress pathway within testicular cells were described in Figure 2.

Nowadays several epidemiological and clinical tests reported that semen quality represents a clear decline over the year. Animal studies are widely used and are often the first sight of the impact of EDCs on reproductive or developmental effects in humans. Xenobiotics connotatively alter human reproduction by affecting the development of gonads and gametogenesis. In particular, spermatogenesis is the process by which sperm cells are produced in the testes, and EDC exposure can potentially disrupt this process, leading to spermatogenesis failure or impaired sperm production (108). The spermatogenic cycle takes 74 days in humans (35 days in mice and 52 days in rats). This process may be affected by chemicals disruptors at any stage of cell genesis, giving rise to declined sperm parameters: counts, morphologically abnormal sperm, impaired stability of sperm chromatin or sperm DNA damage (109). This study shows that the number of spermatogonia affected will increase with repeated exposure to xenobiotics, which can only be detected by histopathology. Subsequently, all other spermatogenic cells are undifferentiated, altered and then depleted, which may result in the decrease of testis weight and sperm count (109). The mechanisms underlying these disruptions are complex and can involve several pathways including hormone disruption (110), Sertoli cells dysfunction, Leydig cells dysfunction (111), epigenetic changes (112), oxidative stress (113, 114), and disruption of blood-testis barrier (115, 116).

The main effects of EDCs on spermatogenesis and male fertility that have been demonstrated are the structural damage of the testis (vasculature and blood-testis barrier) and the harm of Leydig and Sertoli cells (4). Bahri et al. (117) found a significant reduction in the semen quality of North African men in a retrospective study of 20,958 sperm analyses (117).

Semen volume (mL), percentage of motile sperms, sperm concentration (millions/mL) and percentage of sperms with normal morphology are by far the major questionable factors for male fecundity. Most occupational semen studies compared semen quality between exposed and unexposed workers. The exposed participation has 40–60% lower semen quality than controls. This may introduce the effect of EDCs in fertility problems (118). A meta-analysis from 64 papers (8) showed a negative association between pesticides exposure as EDCs and sperm characteristics. Therefore, EDCs especially organochlorines and organophosphates affect frequently some sperm parameters like total sperm count, sperm motility, and sperm morphology (8). The investigation of 2,122 patients reported an association between altered sperm parameter and occupational pesticides exposure. They found that semen volume, motility, and vitality were decreased in men exposed to pesticides (119). However, they suggested that some pesticides could affect post testicular sperm maturation, in which epididymis, prostate, and seminal vesicles are particularly involved (119). On the contrary, our study analyzed a total of 671 men living in a region (Picardy region of France) highly exposed to pesticides and revealed no significant impact of pesticides exposure on some conventional sperm parameters (86). Delgouffe and colleagues highlighted important findings in their study published in 2023. The investigation regarding the impact of gonadotoxic treatment on testicular tissue, spermatogenesis, and reproductive hormone disruption. The outcome reported a reduced testicular volume in 9 among 12 treated patients, that can indicate testicular damage or dysfunction. Additionally, a total of 10 patients showed some degree of reproductive hormone disruption. This disruption can explain the disrupting impact of the gonadotoxic treatment on the endocrine system. In contrast, one of the most remarkable findings of this study is that, despite the gonadotoxic treatment and the potential adverse effects on the testes, ongoing spermatogenesis was observed in 8 out of the 12 patients (120).

Interestingly, primary testicular failure known as primary hypogonadism, occurs when the testes are unable to produce enough testosterone and other hormones despite normal or elevated levels of gonadotropins like FSH (serum FSH levels ≥10 IU/L). Based on this concept, the study of Kanbar et al. (121) revealed a higher incidence of primary testicular failure after gonadotoxic treatment (121).

Plastic Derived EDCS are common in domestic use. DHEP and BPA are currently found in urine of men and they negatively impact sperm quality (sperm count, morphology and motility) (82). A systematic review and meta-analysis of 7,825 individuals and 479 individuals, respectively, performed the impact of up to 12 families of EDCs on male infertility (semen quality, DNA integrity and pregnancy rate or fecundability), the data analysis showed a high heterogeneity among studies. The metanalysis revealed a positive association between polychlorinated biphenyls (PCB153) exposure and sperm count, but no association between bisphenol A, PCB153 and the rest of sperm parameters analyzed (122). After the Elfe study conducted in 2011 to measure the exposure levels of bisphenol and phthalates in women who gave birth in France (123, 124). The Esteban study aimed to estimate the bisphenols and phthalates exposure of children (n = 1,104, 6–17 years-old) and adults (n = 2,503, 18–74 years-old) of the French population between 2014 and 2016 (29). This study was based on the quantification of these compounds and their metabolites in urine [phthalates metabolites are almost completely excreted via urine (125, 126)], mainly by liquid and gas chromatography followed by mass spectrometry. Results were represented as reference values of exposure (RVs) that reflect the concentration of the chemical substance the population is exposed to. Results showed higher RVs for phthalates than bisphenols in children and adults. Phthalates metabolites with the highest RVs were the mono-isobutyl phthalate (MiBP) and the mono-isobutyl phthalate (MEP) (129 and 402 μg/L, respectively, in adults’ urine; 162 and 492 μg/L, respectively, in children’s urine). Exposure to phthalates was also evaluated in tap and raw water across 101 French departments (from November 2015 to July 2016). Dibutyl phthalate (DBP) and diethyl phthalate (DEP) were, respectively, the most frequently detected pollutants in tap water and raw water at a maximum concentration of 1,300 ng/L and 255 to 406 ng/L (less than ten times the limits quantification LOQ) (127).

In vitro exposures of sperm for 90 min to phthalate at different concentrations (1, 10, 100, and 500 μg/mL) showed that phthalate significantly reduces the sperm motility and hyperactivity by preventing the sperm ability to generate ATP. Also, short-term phthalate exposure (>10 μg/mL) generate abnormal capacitation and the acrosome reaction by increasing protein tyrosine phosphorylation via a protein kinase-A-dependent pathway. Otherwise, phthalate exposure (particularly 10 μg/mL) significantly affected fertilization and embryonic development. The findings showing by Amjad and his colleagues in 2021 indicate that the phthalate mixtures negatively affected sperm motility, capacitation and acrosome reaction, which provoked a poor fertilization rates and defect embryonic development (128). Plastic Derived EDCs are common in domestic use. DHEP and BPA are currently found in urine of men and they negatively impact sperm quality (sperm count, morphology and motility) (82).

While genetic factors certainly play a crucial role in semen quality decline, environmental factors, including exposure to EDCs like triclosan (found in antibacterial soaps, toothpaste, hand sanitizers, and even some cosmetics), have been hypothesized to disrupt the endocrine system and potentially affect the development and function of the male reproductive system (129). A prospective study in China including 443 couples reported that increased levels of triclosan in male urine have been linked to reduced fecundity (OR 0.77; 95% CI, 0.62–0.97). Furthermore, there was a notable rise in the risk of infertility, indicated by an odds ratio (OR) of 1.6 (95% CI, 1–2.6) (129).

In typical and healthy spermatozoa, the chromatin is presented as a sequence of nucleotides well compacted and devoid of DNA strand breaks or base mutation (130). During chromatin compaction (the processes that give a higher DNA stability and protect the double strand in its path through the male and female reproductive tracts) (131), the protamine replaces 85% of histones. Any abnormalities in protamine replacement, deficiency and mispackaging can provoke an error in DNA compaction and lead to error in spermiogenesis process which contributes to premature nuclear condensation and spermatozoa immaturity (132, 133).

The DNA fragmentation is a break at the single DNA strand defined as single-strand DNA breaks or at the double DNA strands and termed as double-strand DNA breaks, generating free 5′–3′ ends affecting DNA sequences (134).

As mentioned in literature, the causal factors of DNA fragmentation are diverse. They include pathology like varicocele, lifestyle, environmental and occupational exposure to pesticides. These factors increase ROS levels in cells which lead to an oxidative stress. The ROS attacks the nucleoproteins, provoke a lipid peroxidation and a damage in DNA (fragmentation and oxidation) (3). In addition, chromatin compaction defects make the spermatozoa more sensitive to the attack of ROS (135). Many EDCs have been found to affect male fertility at multiple levels, including sperm production, quality, and morphology, as well as the structure and function of the male reproductive system (82). Exposure to EDCs has been associated with a decline in sperm quality and quantity, as well as an increase in DNA damage in sperm (136). Preclinical studies with male rats showed that exposure to BPA increase the lethal mutation rate during fourth and sixth week of mating intervals at 5.0 mg/kg body weight dose of BPA. The results indicate this latter impacts the germ cell and damages the sperm DNA (24). A study assessed the impact of phthalates on 379 by evaluating the men urinary concentrations of phthalate metabolites and the sperm DNA damage. The results showed that sperm DNA damage was associated with diethyl phthalate’s metabolites [Monoethyl phthalate and Mono-(2-ethylhexyl) phthalate] (137). In addition, in 2011, Meeker and collaborators demonstrated the association between the urinary concentrations of parabens, serum hormone levels, semen quality parameters, and sperm DNA damage, reporting that there is no significant association between the urinary parabens and hormone levels or conventional semen quality parameters, but its positively associated with sperm DNA damage (83). Our retrospective study stated before revealed a significant decrease in sperm vitality and motility (progressive and non-progressive) in the exposed group. These results emphasize the negative impact of pesticides exposure on sperm DNA integrity. However, the sperm DNA integrity analysis includes the sperm DNA fragmentation demonstrating a significant increase of DNA fragmentation index in the group exposed to pesticides compared to the non-exposed group (86). Another study suggests that even smoking and alcohol consumption have detrimental effects on spermatogenesis through oxidative stress-induced changes. The findings show an increased catalase (CAT), superoxide dismutase (SOD) and glutathione reductase (GR) activities in the exposed group as well as the significant increase of DNA fragmentation. These increased enzymes activities suggest that the testicular cells are responding to elevated oxidative stress caused by smoking and alcohol that are environmental factors we are exposed to in addition to EDCs (138).