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Fertility Alterations Related to Endocrine Disruptors

Introduction

The objective of this essay is to review the endocrine disruptors’ effects on the reproductive system, and whether it is a clinical concern in domestic animals. We will discuss the physiological effects in male and female animals, and dive deeper into the concerns related to different species. The ways of exposure and accumulative capacities of the endocrine disruptors will also be taken into consideration.

Table of Content

Endocrine Disruptors

Endocrine disruptors (ED) are defined as substances found in our environment with the ability to alter the physiology of the mammalian or avian endocrine system. Both adult animals and developing organisms may experience harmful and long-lasting damage. Among these are developmental disorders, altered metabolic balance and reproductive problems. There is a broad spectre of ways of exposure, and they have an effect in really small doses. The endocrine disruptors may be incorporated orally, penetrate through skin or through mucous membranes. Offspring may receive disruptors through the placenta, with breast milk or into an egg. They are found in minerals (e.g. lead, mercury), micotoxins (e.g. zearalenon), agriculture (e.g. insecticides), industry (e.g. phthalates, BPA), among others (see Figure 1).

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The endocrine disruptors may disturb the hypothalamic-pituitary-thyroid, hypothalamic-pituitary-gonad and hypothalamic-pituitary-adrenal axis in several ways. They may interfere with the synthesis, release, transport or degradation of hormones, receptors or signalling cascades of target cells, or the hypothalamus itself. The biochemical properties of mitochondria can be affected, as well as altered metabolic rate and gene-expression. In this article, we have chosen to focus on some of the most common endocrine disruptors eliciting a concerning impact on the male and female reproductive systems.

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Brief Description of Specific Endocrine Disruptors

Methoxychlor (MXC)

Methoxychlor (MXC) is an organochlorine pesticide. It is used as a replacement for DDT, another organochlorine known for its infamous, destructive impact on the environment. MXC metabolites possess estrogenic, anti-estrogenic and anti-androgenic properties (Gaido et al., 2000).

Genistein

Genistein is a flavonoid phytoestrogen found in several plants, including soy beans, medicinal plants, and coffee. It has been proven that genistein possesses estrogenic properties in several mammalian species. (Whitehead et al., 2002).

Bisphenol A (BPA)

Bisphenol A (BPA) is a man-made monomer used to produce polycarbonate plastic and epoxy resins (Markey et al. 2002). Many studies have shown that BPA possess estrogenic properties, likely due to shared similarities in their chemical structure (indicated in Figure 3). It is to be found in i.e. plastic bottles, food containers and animal cages and has been spread to the environment through these common objects. Consequently, it proposes a huge potential health risk concerning, among several aspects, mammalian reproduction (Hunt et al., 2003).

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Vinclozolin

Vinclozolin is a fungicide, commonly used to control diseases on fruits, berries and vegetables. In addition, it is used on the turf on golf courses. Vinclozolin has known anti-androgenic activity (Kelce et al., 1994).

DDE

Dichlorodiphenyldichloroethylene (DDE) is a common breakdown product from DDT. Due to the extensive utilization of DDT and DDE in society and agriculture during the 1900’s, they are still widely found in animal tissue samples. DDE is especially concerning as it is rarely excreted from the body once it’s consumed. The exception is breast milk, indicating that accumulation in infants commence almost directly post-partum. Less research is conducted on DDE’s impact on the reproductive system in mammals. However, it is proven to possess anti-androgenic effects (Andersen et al., 2002).