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Sunday, February 22, 2009

Ron Duncan: Are endocrine disruptors reducing human sperm count, killing off the species?

"You have to read this," my brother said. "It shows how the human race is dying out." Dubious, I opened the book that he offered me and stared incredulously at a little-known statistic stating that "average male sperm counts dropped by almost fifty percent between 1938 and 1990." The book was entitled "Our Stolen Future" and was my first introduction to class of chemical compounds known as "endocrine disruptors" and the effect that they are having on our fertility and the fertility of many species across the globe.

The discovery that human sperm counts had been steadily dropping occurred in 1992, when the results of Danish researcher Dr. Niels Skakkebaek's meta-analysis on male fertility was published in the British Medical Journal. Analyzing the findings of every study on sperm count that had occurred since 1930, Dr. Skakkebaek uncovered this surprising trend when he realized the combined evidence of all these studies pointed to an average decline in male sperm count by 1 percent per year. In the aftermath of the publication of these results, countries across the globe tested the sperm counts of their male populations only to find, in many cases, confirmation of Dr. Skakkebaek's conclusions. In the most recent of such studies published last year, Italian researchers at the University of Pisa discovered that the number of active sperm in Italian men has dropped by more than 15 percent in the last 30 years.

Puzzled, scientists were at a loss to account for the trend, until further investigation indicated the decline in fertility rates to be geographically dependent, and thus tied to environmental factors.

Fortunately for Americans, several studies in the mid-1990s revealed sperm counts of American males in New York, L.A. and Minnesota to be increasing, while those of their European counterparts were moving in the opposite direction.

When alarming data on animal infertility emerged that coincided with the human trend, scientists began to look to endocrine disruptors as the likely culprit.

Endocrine disruptors are so-named because they disrupt our endocrine system, a system that produces and regulates our hormones, controlling our body's growth, metabolism, and sexual function and development. Endocrine disruptors act as synthetic hormones, throwing off our hormone levels by mimicking or blocking the natural hormones in our bodies. Although most research has focused on endocrine disruptors that imitate the female sex hormone estrogen, others are found to simulate testosterone, our metabolic hormones and more.

The adverse effects that endocrine disruptors can have on human fertility first came to light in the 1970s as a result of the scandal surrounding the pregnancy drug diethylstilbestrol, or DES. In 1938, when scientists discovered that the body mistook DES for the hormone estrogen, it was hailed as the new wonder drug. Believing the more estrogen the better, doctors throughout the country in the 1940s, '50s and '60s began prescribing DES to their pregnant patients to prevent miscarriages and other pregnancy complications.

Ironically, DES had the opposite effect, as women who had taken DES during pregnancy were more likely to miscarry, have premature children or have babies who died during infancy. However, it was not until the late 1960s and the early 1970s, when a rash of young women began dying of a hitherto rare form of clear-cell vaginal cancer, that the true danger of DES was exposed. It turns out that these young women, most in their late teens and early twenties, all had one thing in common: their mothers had taken DES during pregnancy at a critical time for their development. Other female "DES babies" were found to have fertility problems, including misshaped sexual organs. In males exposed to DES in the womb, the consequences, though not as clear-cut, have been revealed by some studies to include higher rates of underdeveloped testes, stunted penises, undescended testicles, and abnormal sperm.

While doctors no longer prescribe DES, the disturbing truth is that all of us, including, of course, pregnant women, continue to be exposed to endocrine disruptors in our environment, and to ingest them in our food and water. Plasticizers such as bisphenol-A or BPA, found in plastics labeled with the number 7; pesticides, including DDT; and chemicals such as PCBs, formerly used in coolants, lubricants, paints and sealants, are among the endocrine disruptors present in our environment that mimic estrogen in the human body.
These compounds are so pervasive that they have been found in varying levels throughout the world, with high concentrations discovered in seals, polar bears and other marine life currently experiencing fertility problems in areas as remote as Svalbard in the Arctic Circle.

In other words, not only are these substances pervasive, spreading easily across the globe, but they are long-lasting, the evidence being that DDT and PCBs were outlawed decades ago, but still persist in our environment, threatening our own health and the health of other species. Moreover, the number and variety of endocrine disruptors in our environment is unknown since the FDA and other government regulatory agencies to do not test the more than 2,000 chemicals that come on to the market each year to determine if they are endocrine disruptors before releasing them upon the unsuspecting public.

Those at greatest risk to the potential ill effects of endocrine disruptors are fetuses and newborn babies because of the important role that hormones play in development. A prime example is the function of hormones in sexual development. All babies, regardless of whether they have XX chromosomes girls or XY chromosomes boys do not begin to develop their gender until around the seventh week of life for males or the third or fourth month females. Until the time of that important transformation, every fetus is equipped with a pair of unisex gonads that have the potential to transform into either the male or female sexual organs. For boy babies, at the seventh week, the Y chromosome signals the development of the unisex gonads into testes and the rest of the process of gender development is directed by the male hormones produced by those organs. For females, the third or fourth month is when the male-potential Wolffian ducts whither and disappear and, as time goes on, estrogen helps guide the proper development of the ovaries. Things can go wrong if hormone levels are off. For example, male babies that don't receive a strong dose of testosterone at the right time will become hermaphrodites or their testicles will not descend.

Because proper sexual development, particularly in males, is reliant on receiving the correct levels of hormones at a precise moment, many scientists are concerned about the impact of fetal exposure to hormone mimicking elevated hormone levels or blocking lowered hormone levels endocrine disruptors. It has been found that even small doses of synthetic hormones can have serious and lasting consequences. As a result, it is recommended that pregnant women in particular limit their exposure to these harmful substances as much as possible.

Here are some tips for avoiding endocrine disruptors:

* Eat organic food and consume most of your protein from vegetable sources. Because endocrine disruptors "bioaccumulate" in animals, eating animal fat including fish can expose you to higher doses of these chemicals.

* Avoid foods that have been exposed to plastics and don't cook your food in plastic containers, which can leach plasticizers into foods when heated.

*Avoid drinking from plastic water bottles, especially those labeled with the number 7 use stainless steel instead, and limit consumption of canned foods. There is a plastic coating inside can products that reduces metallic taste, but has been shown to leach plasticizers into food.

* Never feed your baby using a plastic bottle, many are plastic No. 7, which contains BPA; always opt for glass bottles.

* Install a filter on your taps and showerhead to strain out pesticides and other chemical compounds from your water.

* Avoid dioxin also an endocrine disruptor by limiting exposure to smoke, animal fats and chlorinated products.

* Limit exposure to chemicals in general.

So, is the human race dying out? The good news is, not yet. Look around; we have 6.7 billion people in the world! Even with the reduced male sperm count, men still have a sufficient amount, on average, of fully functional sperm for fertility. An adequate sperm density is considered to be around 20 million per milliliter, and even those Italians in the study cited above had a density of 60 million per milliliter.

However, the statistics surrounding fertility and the effects of endocrine disruptors should serve as a warning signal. If we don't take serious action to combat the problem, my brother may end up being proved right.


Wednesday, February 18, 2009

Men Must Contend With a Biological Clock, Too

Older males face higher risk of fathering children with medical problems, research finds

It wasn't all that long ago that any suggestion that a man had a "biological clock" like a woman, and should father children sooner rather than later, would have been given short scientific shrift.

Not anymore. Today, a growing body of evidence suggests that as men get older, fertility can and does decline, while the chances of fathering a child with serious birth defects and medical problems increase.
Some studies have linked higher rates of serious health problems such as autism and schizophrenia in children born to men as young as their mid-40s.

And doctors and researchers are busy trying to figure out how men who choose to delay fatherhood -- either by choice or necessity, such as a lack of a partner -- can offset the effects of their biological clocks as those clocks wind down.

Interestingly, problems with reduced fertility can start long before middle age, said Dr. Harry Fisch, one of the pioneers in the field in male fertility and director of the Columbia University College of Physicians and Surgeons' Male Reproductive Center, in New York City.

"We know after age 30, testosterone levels decline about 1 percent per year," said Fisch, author of the book The Male Biological Clock.
Research done at the University of Washington has found that "as men age, DNA damage occurs to their sperm," said Dr. Narendra P. Singh, a research associate professor in the department of bioengineering, who co-authored a study on the subject.

Several other studies point to problems in the offspring of older fathers, as well as older men experiencing fertility problems.
For instance, Fisch and his colleagues found that if a woman and a man were both older than age 35 at the time of conception, the father's age played a significant role in the prevalence of Down syndrome. And this effect was most detectable if the woman was 40 or older -- the incidence of Down syndrome was about 50 percent attributable to the sperm.
Other researchers have found that children born to fathers 45 or older are more likely to have poor social skills, and that children born to men 55 and older are more likely to have bipolar disorder than those born to men 20 to 24 years of age at the time of conception.

On other fronts, researchers at Mount Sinai School of Medicine in New York City found that children of men aged 40 or older were about six times more likely to have autism. Still another study found that the children of fathers who were 50 or older when they were born were almost three times more likely to be diagnosed with schizophrenia.

Fisch is now focusing much of his attention on encouraging men to assess if their biological clock is ticking faster than it should. For instance, men who are overweight or obese tend to have more fertility problems than healthier men.

"It turns out that if you are too heavy, you have a lower sperm count," he said, adding that excess body fat causes testosterone levels to decline. The good news: Losing weight helps them return to normal.
Singh advises older men who want to become fathers to pay attention to lifestyle issues and practice healthy habits that will, in turn, keep their sperm healthy. That particularly means no smoking and no overuse of alcohol, he said.

Both Fisch and Singh said they don't think there's a "cutoff" point for fatherhood. And they said it's difficult to pinpoint the "ideal" age to father a child, especially since many couples today are marrying later and delaying starting a family.
But Fisch did say, "The sooner, the better."