Endocrine Disruptors Part 1

According to the Environmental Protection Agency's definition, endocrine disruptors are chemicals that "interfere with the synthesis, secretion, transport, binding, action, or elimination of natural hormones in the body" and from an environmental health standpoint, they are of major concern. Why? Because, hormones are naturally occurring substances, produced in the body, which act as messengers, sending signals that tell genes, cells, and systems to turn on, turn off, increase production, or decrease production. Most are associated with the endocrine system, which includes the pituitary, pineal, thyroid, parathyroid, and adrenal glands as well as the pancreas, ovaries, and testes. Endocrine glands and organs produce and release twenty different hormones that are critical in regulating growth and development, mood, tissue function, and reproduction. Like a key and lock, each hormone (the key) is associated with specific genes or cells that have receptors (the lock) for that hormone.

Let's take a closer look at how hormones influence reproduction: Just two cells, a sperm and an egg, each carrying a set of instructions embedded in molecules of DNA, join together and direct the choreography of life: Forty hours after fertilization, the cells have divided four times; by three days, twelve cells have formed. The second week, the cells begin differentiating, and by eight weeks, the organs have begun forming and the heart begins beating. At birth those two cells have transformed into trillions.

If all goes well during the development dance a healthy baby enters the world, but this dance is intricately complex—a blend of eloquent ballet, some wild cha-cha, a turn or two of twist and shout, and a bit of polka. It relies on a mind-boggling set of exquisitely timed biochemical processes, controlled by unfathomably minute quantities of hormones. These hormones act as conductor, keeping the band on beat. Just one missed beat or crossed step, and the dancers—those emergent cells that are dividing and transforming into eyes and ears, fingers and toes, livers and lungs—go astray, and the pregnancy ends in miscarriage, or a child born with birth defects or chronic health problems such as asthma, ADHD, or autism. Missed beats and missteps also increase the odds of adult-onset health and reproductive problems, or may even cause problems in the children and grandchildren of generations to follow.

Unfortunately, this dance is one that clearly seems to be going off beat more and more often: impaired fecundity (or the inability to conceive or carry a child to term) is a problem that affects at least 12% of women and their partners who are of childbearing age and trying to get pregnant, and that number may be quite conservative because it’s based on the number of women seeking help at fertility clinics, thus losing count of those who can’t afford to seek such help, or who choose not to.

Your first thought might be, “Well, women are waiting longer to conceive, so its logical that conception is down,” but that assumption caves under scrutiny: "Fertility levels have declined 50% worldwide between 1950 and 2000," Shanna Swan, a reproductive epidemiologist at the University of Rochester Medical Center, said at a recent conference (held in January at the University of California San Francisco) on Environmental Challenges to Reproductive Health and Fertility. “The most disturbing news is that the greatest increase in infecundity is among women under 25. These women and their partners should not be subfertile.”

What Swan, and dozens of other scientists presenting at the conference pointed to as a likely driver of this trend is endocrine disrupting chemicals--and there are thousands of them.

Coming tomorrow: Part 2