196 Autism and Exposure to Environmental Chemicals
the fetuses to any abnormal amount of sex hormones may interfere with normal
development. As an example, we show below the normal parameters of testos
terone or estrogens in a developing male and female from developing fetus to
childhood.
There is a long history of research investigating the effects of EDCs in male
reproductive health in humans and other lifeforms [7]. One of the best‐studied
endocrine based examples is exposure to a potent synthetic nonsteroidal estro
gen, diethylstilbestrol (DES), taken during pregnancy by women from the
1940s to 1975 to prevent miscarriage and other complications. DES is an estro
genic chemical that binds with high affinity to the ERs, ERα and ERβ, which
play an important role in adiposity regulation as well as central and peripheral
energy balance [97]. DES was prescribed at doses from <100 up to 47,000 mg,
depending on the stage of pregnancy (the higher the pregnancy stage, the
higher the dose). Its use was discontinued when a subset of exposed daughters
presented with early‐onset vaginal clear‐cell adenocarcinoma [98]. A 40‐fold
increase in risk was found compared with unexposed individuals [99].
Eventually, it was determined that the DES‐exposed offspring of both sexes had
increased risk for multiple reproductive disorders, including cryptorchidism in
male offspring, and numerous other diseases [100]. Furthermore, emerging
data suggest that there is significantly increased disease risk in grandchildren
[101]. Of note, the DES scenario first suggested the possibility that synthetic
estrogens or other potentially environmental estrogenic synthetic chemicals
can affect not only female but also male reproductive health. This discovery
prompted a broad evaluation on how hormone exposure affected human
health, eventually leading to a better understanding of how EDCs, especially
those that are anti‐androgenic chemicals, may play key roles in the develop
ment and maintenance of male health. Therefore, not surprisingly, a plethora
of examples is emerging for increased disease susceptibility later in life as a
function of developmental exposures to EDCs that include bisphenol A (BPA),
phthalates, PCBs, pesticides, dioxins, and tributyltin (TBT), and thousands of
other synthetic chemicals that are being introduced almost every day and
whose effects on the human body are still unexplored. Among the most serious
ones are found in fragrances that can reach human fetuses without anyone
suspecting their adverse effects (reviewed in Refs [7,53]).Why Is It Important To Look at EDCs and Their Potential Effects
on Our Next Generations?
The endocrine glands are distributed throughout the body and produce
the hormones that act as signaling molecules after release into the circulatory
system. As shown in Figures 7.7 and 7.8, development, physiological processes,
and homeostatic functions are regulated and maintained by hormones. The
hormonal regulation and maintenance is conducted like a giant orchestra