Edinburgh
— In 1991, a Danish scientist presented the results
of a study to a World Health Organisation
<http://www.who.int/>
conference, showing that the sperm counts of Western men
had fallen by about a half over the previous 50 years.
Professor Niels Skakkebaek of the University of
Copenhagen <http://www.ku.dk/>
could offer no explanation for the findings, but neither
could he dismiss them as a mere statistical fluke. More
than a decade later, scientists are still trying to
explain the apparent feminisation of modern man.
There is now mounting
evidence that something quite serious is happening to
male fertility, and not just in sperm counts. It
encompasses a range of disorders of the male reproductive
system, and medical researchers have even coined a name
for it - testicular dysgenesis syndrome.
The syndrome is a
collection of disorders that manifest themselves at one
of two stages in life. At birth, it appears as
cryptorchidism <http://en.wikipedia.org/wiki/Cryptorchidism>
- the incomplete descent of the one testis or both testes
into the scrotum - or a disorder of the penis in which
the opening does not develop at the tip, a disfigurement
called hypospadia <http://en.wikipedia.org/wiki/Hypospadias>.
Later in life, after adolescence, testicular dysgenesis
syndrome can appear as more generalised disorders such as
low sperm counts, infertility, or cancer of the
testes.
There is ample data to
suggest that these disorders are on the increase.
Cryptorchidism is the most common congenital malformation
in children of either sex, affecting between 2 and 4 per
cent of baby boys, and hypospadias are the second most
common congenital malformation in children. Low sperm
counts now affect up to one in five young men, and
testicular cancer <http://en.wikipedia.org/wiki/Testicular_cancer>
is the most common cancer of young men, and its incidence
has increased steadily over the past 60 years. In fact,
were it not for the fact that testicular cancer is so
curable, it would be the biggest killer of young men
after road-traffic accidents, according to Dr Richard
Sharpe, a male-fertility specialist at the Medical
Research Council's Human Reproductive Sciences Unit in
Edinburgh <http://www.nhmrc.gov.au/>.
Sharpe is one of several
experts in the field who believe that there could be a
common basis for all these different problems of the male
reproductive system. He suggests that all the disorders
stem from a problem arising at the key stage in the
development of the male foetus during early pregnancy.
"From epidemiological studies, we know that each of the
disorders is a risk factor for all the others, and that
they share several pregnancy-related risk factors,"
Sharpe says. "Most importantly, we know that they share
hormonal risk factors, in particular anything that
interferes with the production or action of androgens and
testosterone [the male sex hormones] during the
sexual differentiation process of the foetus that occurs
in the womb."
In other words, the
suggestion is that there is something happening early in
the development of the male foetus that interferes with
the key steps enabling it to develop into a healthy,
fertile male. Ever since Professor Skakkebaek made his
discovery on sperm counts, environmentalists have
suggested that it could be "gender-bending" chemicals -
endocrine disrupters - in the environment that are the
cause of the gradual feminisation of men
<http://en.wikipedia.org/wiki/Endocrine_disrupting_chemicals>.
But despite intense research to find these endocrine
disrupters, the precise reasons for the problems have not
so far been identified.
Some scientists believe
that the culprit may just as likely be a change in
lifestyle, rather than exposure to some new environmental
chemical. John Ashby, from the Syngenta Central
Toxicology Laboratory in Macclesfield
<http://www.syngenta.co.uk/>,
says that the focus on an environmental cause may be
quite wrong. "The human [reproductive] conditions
cannot at the moment be associated with a named
chemical," says Ashby. "There are many lifestyle changes
that could be contributing to these conditions, for
instance increased smoking among young women."
Another possible
lifestyle factor that could be playing a role is the
significant increase in the intake of dietary fat over
the past 50 years. Fat is linked with oestrogens - the
female sex hormone - and more fat means more oestrogens,
which means a possible increase in the risk of
interference with the proper development of male
reproductive organs. "The trends on dietary fat are up,
and the implications are great for endocrine disruption,"
says Ashby.
Nevertheless, work on
animals has led to the discovery of some chemicals in the
environment that could be playing an important role.
Sharpe cites his work on chemicals called phthalates,
substances used by industry to soften plastics. He has
been able to create a set of disorders in laboratory
animals that mimic human testicular dysgenesis syndrome
by exposing pregnant mothers to certain phthalate esters
at a key stage of foetal development.
"Phthalates are the most
common environmental chemical. They are in the air around
us," says Sharpe <http://en.wikipedia.org/wiki/Phthalates>.
However, he points out, it is too early to jump to the
conclusion that this is the cause of the problem. "At
present, doses that are 100- to 500-fold higher than the
highest reported human exposure are required to induce
such effects, and we do not have any proof that
phthalates can induce such effects in humans," he says.
"Nevertheless, phthalates are everywhere in our
environment, we are all exposed, and the highest exposure
appears to be in young women of reproductive
age."
But although the jury is
out in terms of what is causing the reproductive problems
among humans, the same is not the case for the
feminisation documented among wildlife, according to
Professor Peter Matthiessen of the Centre for Ecology and
Hydrology <http://www.ceh.ac.uk/>,
Windermere. "People are cautious about saying that there
are definite effects on humans, but we have hard evidence
for effects on wildlife in all groups, from invertebrates
to mammals," he says. "It's a real-world issue, not just
a theoretical worry. It's actually happening. The effects
range from relatively trivial biochemical changes,
probably of no ecological significance, to huge changes
in populations and communities of organisms."
Most work has centred on
the rise of hermaphrodite fish in British rivers, which
seems to have happened as a result of the increase in
natural and synthetic oestrogens pouring into the aquatic
environment from sewage effluent. "Most of the effects
seem to be occurring in the aquatic environment. We're
not sure why. It might be due to not enough work being
done in the terrestrial environment, but I think it is a
genuine effect and something do to with the exposure of
water-breathers," says Matthiessen.
The contraceptive pill
being flushed down the toilet is one obvious reason for
the increase in oestrogens in the environment. Natural
oestrogens break down relatively easily, but synthetic
oestrogens are designed to withstand the rigours of the
human intestine - the same traits that prevent them from
being broken down by microbes in sewage-treatment
works.
The crucial question is
whether this environmental chemical, or any others
suspected of being endocrine disrupters, are actually
getting back into the human food chain to affect foetal
development in pregnant women.
Richard Sharpe is keen to
assert the importance of not jumping to conclusions. "I'm
concerned that people run away and say that because we
are investigating something, and because it can cause a
similar disorder in animals, then it must cause it in
humans," he says. It is in everyone's interest to focus
on the disorder rather than on the potential culprits, he
says. "If we assume guilt, the real culprit may be able
to carry on causing harm while we get
side-tracked."
Although scientists have
made great strides in understanding endocrine disruption
since Professor Skakkebaek's sperm-count study was first
brought to the public's attention in 1991, they have
still a long way to go before they can explain what is
actually happening to the fertility of the human
male.
