Ladies … if you are considering a partner to have a child with, check his bone structure!
Intriguingly a new study by researchers at Columbia University Medical Center provides the first evidence that the skeleton is a regulator of reproduction.
Lead researcher Dr Gerard Karsenty and his team have unveiled that the skeleton acts as a regulator of fertility in male mice through a hormone released by bone – osteocalcin.
Until now, interactions between bone and the reproductive system have focused only on the influence of gonads (testes in men, ovaries in women) on the build-up of bone mass.
“Since communication between two organs in the body is rarely one-way, the fact that the gonads regulate bone really begs the question: Does bone regulate the gonads?” said Dr Karsenty.
Of Mice and Men …
Dr Karsenty and his team first noticed that male mice whose skeletons did not secrete osteocalcin were poor breeders.
They then carried out several experiments that show osteocalcin enhances the production of testosterone, a sex steroid hormone that controls male fertility.
As the team added osteocalcin to mice cells that in the human body produce testosterone, its synthesis increased. Similarly, when they injected osteocalcin into male mice, levels of testosterone also went up.
Conversely, when osteocalcin was not present, testosterone levels dropped. This caused a decline in sperm count. As a result, when osteocalcin-deficient male mice were bred with normal female mice, the pairs only produced half the number of litters as did pairs with normal males, along with a decrease in the number of pups per litter.
Now the findings have not yet been confirmed in humans, but Dr Karsenty expects to find similar characteristics in humans, due to other similarities between mouse and human hormones.
If osteocalcin also promotes testosterone production in men, low osteocalcin levels may be the reason why some infertile men have unexplained low levels of testosterone.
Skeleton Regulates Male Fertility, But Not Female
Remarkably, although the new findings stemmed from an observation about estrogen and bone mass, the researchers could not find any evidence that the skeleton influences female reproduction, even though estrogen is one of the most powerful hormones that control bone.
For example, when ovaries stop producing estrogen in women after menopause, bone mass rapidly declines and can lead to osteoporosis.
Sex hormones – estrogen in women and testosterone in men – have been known to affect skeletal growth, but until now, studies of the interaction between bone and the reproductive system have focused only on how sex hormones affect the skeleton.
“We do not know why the skeleton regulates male fertility, and not female. However, if you want to propagate the species, it’s probably easier to do this by facilitating the reproductive ability of males,” said Dr Karsenty. “This is the only rationale I can think of to explain why osteocalcin regulates reproduction in male and not in female mice.”
Conclusion
Personally I found this latest research quite fascinating, in particular the different findings and impact on male and female fertility for seemingly the same biological process.
It is yet another example of how you can marginally increase your odds of getting pregnant by paying attention to a seemingly insignificant detail.
Of course there is a world of difference between the world of mice and men, but if further studies confirm these initial findings in humans it could be a telling factor as to why you can’t get pregnant.
(This post was sent to subscribers in a weekly newsletter on February 23 2011).

