Today's post comes to us from the fabulous Allie Wilkinson, science journalist and blogger at "Oh, for the love of science!" When she told me she had a new paper on anogenital distance...well I had to see it. And when she said she had a VIDEO to go WITH...well it's below the fold. Everyone give a shout out to Allie!
PS: The authors took the opportunity in the manuscript to thank their hardworking, and probably long suffering, medical illustrator. Yes, Matthew Timberlake, our hats are off. How we do thank YOU. You are, in your own way, a Real Man of Genius (TM)
Men, let's talk about that space between your testicles and your anus (taint anus, taint balls - Sci). The length of your member doesn't really have a whole lot to do with your reproductive fitness, but the length of your taint does. It's time to put away the rulers and whip out the digital calipers!
A new study came out in PLoS ONE earlier this week, claiming to be the first assessment of anogenital distance in adult men, as well as the first examination of the relationship between anogenital distance and a man's fertility. I hate to break it to the researchers from Baylor College of Medicine and Stanford University School of Medicine, but you are not the first. A VERY similar study came out two months ago in Environmental Health Perspectives, which Sci so awesomely blogged. As Sci mentioned, anogenital distance is used to sex animals-- shorter for females, longer for males. Anogenital distance has also been studied in human infants, mirroring what we know to be true in the animal world (which makes sense, because we are animals)...but no one had studied this in adults up until recently, which leads us back to the sudden interest in measuring men's taints.
Why do we care how long a man's taint is, anyway? Well, because in the past half century there has been a reported decline in semen quality and male births with an increased rate in male genital abnormalities and testicular cancer....and no one likes cancer, or malformed genitals, or weak semen. Previous studies have shown that in addition to reduced anogenital distance, rodents exposed to certain phthalates (these are special chemicals added to plastics to increase flexibility and durability - Sci) had altered testicular size and Sertoli cell function, cells which nurture the developing sperm cells. Not only that, rodents exposed to endocrine disruptors during critical gestational windows for genital development saw irreparable alterations to penis length, anogenital distance, and testicular weight.
As I mentioned earlier, this study was fairly similar to the study that Sci blogged--the methodology was slightly different, and since there was some question regarding methodology in the comments on that post, I figure we'd go into the methodology a bit here. In this study, eligible patients were recruited from a urology clinic specializing in reproductive medicine. Patients evaluated for infertility that were over the age of 18 were eligible for the study, and a fertile control group was put together with a group of men that had a prior history of paternity. In order to measure their genitals, the men had to get into a frog-legged position. Oh yes, there are pictures:
(Note to self: Do not read papers on anogenital distance and male fertility while sitting in a busy airport such as Logan. You will unknowingly stumble upon said diagram while surrounded by people.)
How does one get ready for measurement anyway? Well first you lay on your back, and then touch the soles of your feet together, making sure to keep your feet 12 to 18 inches away from your butt. Oh, and you may want to get a Brazilian wax first. Someone is going to have to get all up in your business, and I'm sure they'd appreciate a clean work surface. Once ready for measuring, someone will take a pair of digital calipers to you, and measure from the back of the balls to the anus, which these researchers thought to be a more comfortable, reliable and reproducible measurement than measuring from the base of the penis (Though they don’t say what it’s MORE reliable than...A ruler? Bending over and spreading? - Sci). Penis length was taken as well, and testicular volume was estimated by one examiner (lucky man) who had the room at a balmy 78 to 80 degrees Farenheit, because...well....we all know what happens to the boys when its cold out.
All patients also had two semen analyses performed, and semen analyses were performed manually within an hour of collection. I'm going to assume that the semen samples were also OBTAINED manually, and not with a hands-free, semen-collecting robot (though they are becoming more popular! Coming soon to an artificial insemination clinic near you! - Sci).
The volume, density (millions of little swimmers per milliliter), and motility were recorded and multiplied to determine the total motile sperm count. Hormone assays were also processed for testosterone, luteinizing hormone (LH), and follicle-stimulating hormone (FSH) (all of these are hormones which influence fertility in both men and women- Sci). Finally, statistical analyses were performed, including adjustments for age, race, FSH and BMI.
Most of the men in the study were white males (64%), but even when the the results were broken down by race, the length o' taint differences between fathers and infertile men remained stable, with infertile, childless men having a significantly shorter anogenital distance when compared to fathers. Infertile men also had shorter stretched penis lengths and total testicular volumes than fertile men. All genital measurements seem to be correlated to each other, but those in the know can't stress enough: CORRELATION DOES NOT EQUAL CAUSATION. Semen volume was similar in both fertile and infertile men, but the sperm density, motility and total mobile sperm count were significantly lower for infertile men. In both the unadjusted and adjusted models, anogenital distance and testicular volume were significantly correlated with total motile sperm count and sperm density, and sperm destiny and total motile sperm count increased with an increase in anogenital distance. For every 1 cm increase in taint, add another 4.3 million little swimmers per milliliter and the total motile sperm count increases by 6 million. There wasn't any significant correlation seen between penis length and sperm count, which goes back to my opening statement -- PUT AWAY YOUR RULERS! Women will not judge your marriage and fatherhood potential on the length of your penis...instead, they will base it upon your intelligence, your wit, your dashing good looks....and the length of your taint.
Eisenberg, M., Hsieh, M., Walters, R., Krasnow, R., & Lipshultz, L. (2011). The Relationship between Anogenital Distance, Fatherhood, and Fertility in Adult Men PLoS ONE, 6 (5) DOI: 10.1371/journal.pone.0018973