Male Fertility: Threatened by Common Chemicals?
Over recent decades, epidemiological studies have been reporting troublesome trends in the incidence of human infertility rates. Recent findings suggest that overabundances of xeno-oestrogens or synthetic endocrine-disrupting chemicals (EDCs) interfere with human sperm function and may have a harmful impact on human fertilization. EDCs, omnipresent in food, household and personal care products such as toothpaste, sunscreen, soap and plastic toys notably affect the potency of sperm cells, which may account for the high incidence of unexplained male infertility. People ingest EDCs every day either through food and drink contaminated with them or by absorbing them through the skin by sunscreens and soaps. Therefore this issue raises further concerns about the hidden toxicity of these chemicals deemed safe by toxicology tests.
EDCs are thought to mimic female sex hormones – oestrogens – and in other cases act as anti-androgens, the male sex hormones. Very low levels of EDCs trigger the adverse reactions, which are commonly found within the human body. In addition, there is a “cocktail effect”, when a number of different chemicals work collectively to intensify their individual effects.
These EDCs impair sperm function by directly effecting “CatSper”. CatSper is a calcium channel protein which controls sperm cell’s swimming agility, and its capability to fuse with egg cell to trigger fertilisation. Researchers showed that EDCs – applied at concentrations measured in body fluids – directly open CatSper and, thereby, increase calcium levels in sperm, alter their swimming pattern, and trigger the premature release of digestive enzymes that help sperm to break through the egg coat. EDCs also desensitize CatSper for its physiological ligands. Moreover, endocrine disruptors render sperm less sensitive for progesterone and prostaglandins – two important hormones released by cells surrounding the egg. Thus EDCs may cause problems by drowning out the hormonal signal that sperm cells usually follow to find the egg.
Altogether, it has been specified that EDCs may disturb the precisely coordinated sequence of events underlying fertilization in several ways: the chemicals may evoke changes in swimming behaviour at the wrong time and wrong place, hinder navigation of sperm towards the egg, and hamper penetration into the protective egg coat. Thus it may open up a new dimension of potential effects of common lifestyle or environmental chemicals on male fertility.
Direct action of endocrine disrupting chemicals on human sperm. Schiffer C, Müller A, Egeberg DL, Brenker C, Rehfeld A, Frederiksen H, Wäschle B, Kaupp UB, Balbach M, Wachten D, Skakkebaek NE, Almstrup K, Strünker T.
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