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Maciamo
18-02-11, 12:00
Science Daily : Male Fertility Is in the Bones: First Evidence That Skeleton Plays a Role in Reproduction (http://www.sciencedaily.com/releases/2011/02/110217124909.htm)


Researchers at Columbia University Medical Center have discovered that the skeleton acts as a regulator of fertility in male mice through a hormone released by bone, known as osteocalcin.
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The investigators then did several experiments that show that osteocalcin enhances the production of testosterone, a sex steroid hormone controlling male fertility. As they added osteocalcin to cells that, when in our body produce testosterone, its synthesis increased. Similarly, when they injected osteocalcin into male mice, circulating levels of testosterone also went up.

Conversely, when osteocalcin is not present, testosterone levels drop, which causes a decline in sperm count, the researchers found. 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.
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What the article fails to mention is that osteocalcin acts on bone mineralization and calcium ion homeostasis. In other words, they strengthen both bones and teeth. High levels of osteocalcin are therefore the recipe for a strong skeleton and (large ?) strong, healthy teeth. The link with testosterone makes perfect evolutionary sense, since our male ancestors, who were hunters and warriors, needed strong muscles (developed by testosterone) and bones (built by osteocalcin). Generally speaking, strong bones are required for strong muscles lest the bone break under the muscle pressure.

The increased male fertility may be seen as a by-product of elevated testosterone. But it also explains why women favour virile men for reproduction - not just muscular ones, but those with heavy skeletons and strong jaws and teeth. It is a sure sign of higher male fertility, and we now know why.

Shasta
20-04-11, 03:47
Along the same lines of stronger bones and increased testosterone, recall this study on Dr. Cannell's sight. I suppose the larger skeletal man might be the one that hangs out in the sun frequently.

http://www.vitamindcouncil.org/newsletter/vitamin-d-questions-and-answers-international-edition.shtml


I know of no studies measuring male libido and vitamin D but Dr. Wehr and colleagues, at the Medical University of Graz in Austria, just published a surprising study showing that testosterone levels are directly associated with vitamin D levels (measured with the DiaSorin technique) and testosterone levels vary with the seasons, in concert with vitamin D levels. Furthermore, the men with very low testosterone levels had very low vitamin D levels. This study does not prove, like any association study, that vitamin D increases testosterone levels. It may be that sun exposure in the summer is responsible for both higher vitamin D levels and higher testosterone levels. By the way, the New York Daily News got it wrong, nothing in the Wehr study talks about vitamin D increasing male libido.