Why do Danes have smaller nuts than Finns?

Analyzing the latest research affecting women.
Feb. 24 2010 9:41 AM

The Little Princes of Denmark

Why do Danes have smaller nuts than Finns—are toxins to blame?

Illustration by Charlie Powell. Click image to expand.

It's a source of parental pride when baby Buster needs the size "large" penis ring for his circumcision. Mother and father see their child's life unfold effortlessly: He will be flushed with testosterone, well-hung, and yet (somehow) sensitive to the needs of others—a caring leader of great integrity. But what happens when he comes out with a genital malformation?

If you're Danish, you compare the goods to those of your Baltic neighbors.

Concerned with a recent increase in male genital birth defects plus dropping sperm counts and higher rates of testicular cancer, Danish researchers have spent the last five years ranking their nether regions against those of the Finns. Both countries have excellent registry data, an accommodating research population, and a rivalry dating back to Viking-era tribes hitting one another with clubs. Whose cudgel is bigger? That is the question. Why should you care if you're neither Danish nor Finnish? Because the answer involves environmental toxins that have made their way around the globe.

By all accounts, the Finns are winning hands-down (or up?) in the size wars. In a study of 1,600 babies born between 1997 and 2001, the Danes had smaller testicles than the Finns. Scientists know this because they expertly measured "ellipsoidal volume" and found the Danish package lagging at birth. The differences were even more pronounced after three months, with the Finns averaging three times more testicular growth. When these results were published in the Journal of Clinical Endocrinology & Metabolism in 2006, it was the Scandinavian equivalent of announcing Yale men have smaller nuts than Harvard men. The story "was very much in our media," says lead researcher Katharina Main of the University of Copenhagen. Another study measured baby penile lengths, showing boys with more testosterone had longer lads. "The Finns are doing so much better from every parameter, semen, testes size, and cancer," Main bemoaned.

Before you decide that these joy-stick measuring Scandinavians should just be happy being the tallest, blondest people on Earth, consider: Testicle and penis size, and certainly malformations, are sometimes linked to other measures of health and reproductive success. And the environmental factors at work here are affecting other parts of Western Europe and probably North America as well.

Basically, the bigger the nuts, the more Sertoli cells they contain, and Sertoli cells are the "nurseries" that produce sperm. For years, the Danes have been wringing their hands about declining sperm counts. One study from 2006 found 40 percent of young Danish military recruits had suboptimal sperm levels. In the land of Lego, 7 percent of all live births in 2007 required "assisted" reproduction. (In the United States, it's around 1 percent.) There's gloomy news about other measures of manhood as well. About 9 percent of schoolboys have at least one undescended testicle, compared with 2.3 percent in Finland. This condition, called cryptorchidism, doubles the risk for testicular cancer. And, in fact, Danish testicular cancer rates are about one in 100, about three times higher than the Finnish or U.S. rates.

Also troubling: Danish baby boys with the unfortunate malformations are found to have relatively low levels of androgenic male hormones. It's unclear what this means for their adult health; still, even before their births, something was blocking their androgens from doing their job. But what? The likely culprits were genetic or environmental or some combination thereof. Researchers went back and tested samples from the babies' stored blood and their mothers' breast milk. Danes are known to smoke and drink during pregnancy, but that didn't seem to explain the genital effects. Then other hormone-monkeying suspects turned up at relevant levels: industrial chemicals like polychlorinated biphenols (banned since the 1970s but doggedly persistent in land, water, and food), flame retardants, dioxins, and pesticides like DDT. "It turns out the chemical burden is not the same" for Danish and Finnish baby boys, says researcher Main, who was surprised by the finding. "It's higher here. The higher your burden, as measured in breast milk, the higher the risk of undescended testes."

What does all of this augur for males in the United States? Are they more like the poor shrinking Danes or the lucky strapping Finns? Thanks to our relatively poor data sets, it's hard to say, but we know our chemical burdens are similar to the Danes', and even worse for some compounds like brominated flame retardants, which we continue to use in the United States (most are banned in Europe). One relatively common birth defect here is hypospadias, in which the urethra opens somewhere along the underside of the penis rather than on the tip. It usually requires surgery, and severe cases can lead to problems with sexual function and fertility. Depending on whom you believe, it affects either one out of 125 or one out of 250 male births.

According to a study conducted in England last year, women exposed to hairspray in the workplace have a threefold risk of bearing a son with hypospadias. The study points out that many hairsprays contain phthalates, a common class of chemicals used in plastics and linked to hormone disruption. The Centers for Disease Control and Prevention found a doubling of hypospadias in the United States from 1968 to 1993. More comfortingly, a paper published last year found no increase in hypospadias since then in New York hospitals.    

Other disturbing data regarding chemicals and manliness continues to pile up, however. Testicular cancer is increasing alarmingly in the United States as well as elsewhere, doubling over the past 20 years. It is the No. 1 cancer affecting young men. A recent study linked abnormal sperm to blood levels of PFOS and PFOA, widespread substances used to make nonstick coatings. As with cancer risk, an interplay of genes and the environment is likely meddling with male fertility. Gaining ground is the theory that a chemical or combination of chemicals disrupt the hormones early in life, says UCSF urologist Laurence Baskin. "The exposure has to be in the first trimester, because the penis is a done deal by 17 weeks," he explains.

Testosterone and other male hormones affect not only the genitalia but the brain as well. In a curious study published in November in the International Journal of Andrology, U.S. researcher Shanna Swan measured young boys' tendencies toward traditional "male" play. Those boys who played the least with toy guns were exposed to the highest uterine levels of phthalates, as measured earlier in their pregnant moms' urine. Though no one knows what this might mean for the boys' future behavior, SWAN says such data suggest that "prenatal exposure to pthatlates, even at low environmental levels, can induce profound and permanent changes" in the brain and reproductive organs.

Not every expert buys the argument that it is pollutants that are messing with male hormones. It's a difficult hypothesis to prove in humans, even though the evidence is quite strong in animal studies. Dr. Michael Joffe at Imperial College, London, points out that testicular cancer cases mysteriously started rising in the mid 19th century. The timing means that victims of the disease would have been in the womb before many chemicals became widespread.

Still, it's enough to make a mom wonder about using phthalate-laden perfumes and creams during pregnancy. While we wait for more research on this side of the pond, the Danes have already put in place some of the strongest regulations on chemicals in the world, banning PFOA, phthalates, and a host of other compounds. They'll be keeping a keen eye on how things develop. Or don't.

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