- The 60-year-old in 2003 had about 15 percent less testosterone than the 60-year-old in 1988, according to Thomas G. Travison, Ph.D., lead author of the testosterone study. Sixty was looking like the new 70. Had something happened? Could we be in the middle of some broad biological or environmental change affecting all men simultaneously?
Then in the summer of 2006, Travison attended an Endocrine Society meeting where another researcher, Antti Perheentupa M.D., Ph.D., from the University of Turku, in Finland, presented evidence of a similar decline. The Finnish results suggested the change was happening among younger men, too. A man born in 1970 had about 20 percent less testosterone at age 35 than a man of his father's generation at the same age. "When I saw another group reproducing our results," says Travison, "that was convincing to me that we were seeing a true biological change over time, as opposed to just some measurement error."
Possible causes include obesity and heavy prescription drug use, but there's other interesting stuff going on:
- Increasing numbers of boys are being born with genital abnormalities, including undescended testicles, and urethras that exit in odd places along the penis. In Denmark, 40 percent of young men have a subnormal sperm count, and the rate of testicular cancer is among the highest in the world. In the United States testicular cancer has recently become the most common malignancy among Caucasian men ages 15 to 35. Some researchers have grouped these developments together as "testicular dysgenesis syndrome," or TDS, with "dysgenesis" meaning abnormal development of the male organ.
Mitch Harman M.D., Ph.D., an endocrinologist at the University of Arizona college of medicine and the director of the Kronos Longevity Research Institute, sees the shadow of Silent Spring. Back in 1962, when Rachel Carson published her environmental classic, estrogen-like substances in the insecticide DDT were making eggshells so thin that they were crushed by nesting parents; populations of eagles and other large birds plummeted. And today? Dr. Harman says, "I'm concerned that we're just pouring chemicals out into our environment that are endocrine-suppressing, estrogen-like compounds," possibly causing similar disruptions in human reproduction. The authors of a recent article in the Medical Journal of Australia likewise suggest that from early fetal life onward, male hormonal and reproductive functions are under "xenobiotic attack," meaning chemicals not naturally found in the body appear to be disrupting normal biological development.
For instance, 90 percent of American men have evidence of chlorpyrifos in their urine. This shouldn't be surprising, since up to 19 million pounds of the stuff was distributed across the United States in 1999 alone, much of it in household products like tick-and-flea powder for pets, lawn treatments, and common insecticides. Though residential use is now restricted, chlorpyrifos is still common in agriculture, as well as in some professional applications; for most people, diet is now the main source of exposure. In a recent Harvard study, men with the highest chlorpyrifos exposure typically had 20 percent less testosterone than those with the lowest exposure.
I'll let you read the article if this has piqued your curiosity -- which it should, male or female.