The male reproductive system and its susceptibility to endocrine disrupting chemicals

Abstract

Summary. In the past years, there has been increased interest in assessing the relationship between impaired male fertility and environmental factors. Human male fertility is a complex process and therefore a great variety of sites may be affected by exogenous noxae. Lifestyle factors as well as various environmental and occupational agents may impair male fertility. Many studies have been published reporting on reproductive dysfunctions in male animals and humans. Especially environmental pollutants with endocrine activity are discussed as a possible cause of this detrimental development. Evidence from animal experiments show that substances with oestrogenic and antiandrogenic properties may cause hypospadia, cryptorchidism, reduction of sperm density and an increase of testicular tumours. Many adverse effects on animal male fertility have been documented for phthalates and some chlorinated hydrocarbons such as polychlorinated biphenyls and polychlorinated dibenzo‐p‐dioxins. For other chemicals such as bisphenol A and nonylphenols animal data are conflicting. Environmental pollutants may mediate their effects by receptor binding, modulation of hormone‐regulated mechanisms or direct toxic effects. Data on environmental chemicals and human male fertility are scarce, and risk assessment is mostly based on the results of animal studies. However, there are indications that exposure to endocrine active chemicals during early development may alter hormone responsiveness in adulthood. Furthermore, some of the chemicals are found in fluids that are associated with human reproduction, such as follicular fluid, seminal fluid and cervical mucus. Recent studies suggest a correlation between pesticide exposure and standard semen parameters as well as in vitro fertilization rates.

Investigation of the Effects of Bisphenol A on the Histology and Ultrastructure of Prostate and Seminal Vesicle Glands in Rats

“…These plastics can be used in baby bottles, water storage tanks, or supply pipes (5). It is also used to make epoxy resins, electronics, medical equipments, and dental sealants (6,7). The human population is frequently exposed to BPA through various sources.…”

Phthalates and other additives in plastics: human exposure and associated health outcomes

“…The leading hypothesis for these growing concerns is that certain chemicals, used in plastics to provide beneficial physical qualities, may also act as endocrine-disrupting compounds (EDCs) that could lead to adverse reproductive and developmental effects (NRC 1999). In men, environmental or occupational exposures to EDCs may be associated with or lead to declined reproductive capacity or possibly increased risk of testicular or prostate cancer (Fleming et al 1999;Pflieger-Bruss et al 2004;Toft et al 2004). In fact, a number of studies have suggested the use of circulating reproductive hormone levels (follicle-stimulating hormone (FSH) and/or inhibin B) as a surrogate measure for semen quality or fecundity in epidemiologic studies ( Jensen et al 1997;Uhler et al 2003;Mabeck et al 2005), although other recent studies suggest hormone levels may lack sufficient ability to predict poor semen quality (Dhooge et al 2007;Meeker et al 2007a).…”

Discussion of Bisphenol A as an Environmental Endocrine Disruptor: The Low Dose Effect and Governmental Regulations Concerning its Use and Disposal: A Literature Review

“…(Richter et al, 2007) The issue with BPA is that studies have been published with both no observed effects and significant observed effects in both mice and rats for dosages below the "safe dose". (Pflieger-Bruss et al, 2004) A review published in 2005, (vom Saal & Hughes, 2005) discusses the existence of both results in published studies but proceeds to make several important points regarding the proportions of the opposing results. In the review by vom Saal (vom Saal & Hughes, 2005), the author discusses a large inconsistency in the data with regards to the source of funding for each study.…”

“…A study completed by Pflieger-Bruss et al (2004)outlined the common effects of xeno-estrogen compounds, (i.e. BPA and DES) in animal studies as hypospadias, cryptorchidism, decreased sperm count and testicular tumours.…”

“…While DES is an endocrine disrupting chemical, it can not be considered alongside BPA as it has well documented toxic effects, and as such it is used in all of the studies discussed as a positive control for adverse effects of exposure. The controversial topics of what a low dose is, the concept of environmentally relevant doses (Richter et al, 2007), appropriate animal model selection (Pflieger-Bruss et al, 2004), the need for positive control groups (vom Saal & Hughes, 2005), and the influence of funding sources (vom Saal & Hughes, 2005) are examined in the analysis of these journal articles. The conclusion that there are in fact adverse health effects related to low dose or environmentally relevant exposures is becoming a more prominent finding but still demands significant further research to reinforce this finding.…”