Strong bones, osteocalcin and high testosterone synthesis
A low body fat percentage, strong bones and high testosterone levels are linked, according to endocrinologists at the University of Rome who studied 86 overweight men. Their article in the International Journal of Endocrinology confirms the increasingly popular theory that the state of the skeleton partially determines the amount of testosterone circulating in men's (and probably also women's) bodies.
Osteocalcin & testosterone
A few years ago endocrinologists at Columbia University in the US came up with the theory that the hormone osteocalcin [spatial structure shown above], which is involved in bone growth, enhances the synthesis of anabolic hormones such as testosterone. [Cell. 2011 Mar 4;144(5):796-809.] [J Endocrinol. 2012 May;213(2):107-14.] [Mol Cell Endocrinol. 2014 Jan 25;382(1):521-6.] The researchers were able to show in animal studies that osteocalcin controls the testes, and not only is it partially responsible for determining the amount of testosterone that lab animals synthesise but it also helps determine the animals' fertility.
More recently the researchers at Columbia have extended their theory. In animal experiments they have now shown that osteocalcin also plays a role in insulin synthesis. The more osteocalcin the bones produce, the more insulin the beta cells in the pancreas produce. [J Clin Invest. 2013 Jun 3;123(6):2421-33.]
Fascinating, these theories. But they'd be even more interesting if they were backed up by studies that show that the same thing happens in humans. The Italian research is one of these studies. Sort of.
The figures below summarise the discoveries the Italians made in their obese male subjects. The more fat the men had in their trunk area, the less testosterone there was circulating in their body. The relationship between overweight and a low testosterone level is already known. But the researchers also found that the men with high levels of trunk fat also had less osteocalcin in their blood.
There was a relationship between osteocalcin and testosterone.
In addition, the higher the concentration of osteocalcin, the lower the HOMA. The HOMA is an index calculated on the basis of the amounts of glucose and insulin in the blood. It gives an indication of how well the insulin mechanism is working. The more insulin your pancreas produces, and the more glucose that insulin chases into the cells, the lower your HOMA.
Body fat hampers the insulin mechanism and reduces bone health. As a result of this the secretion of osteocalcin also falls, and therefore also the production of testosterone. That's a very brief summary of the mechanism that the Italians' findings suggest.
Research on the endocrinology of osteocalcin is starting to become interesting for athletes who want to boost their testosterone levels. It was already known that losing excess fat can help, but now it looks as though testosterone levels can also be boosted by strengthening the skeleton.
Connecting the dots
Hmm... suddenly we start to see links.
One of the requirements for strong bones is a diet that contains enough calcium. There is a Turkish study in which calcium supplementation boosts athletes' testosterone levels.
Also important for strong bones: vitamin D. According to epidemiological studies, men with high levels of vitamin D in their blood also have high testosterone levels.
Another factor that plays a role in bone health is magnesium. Epidemiological studies have shown that elderly men with relatively high levels of magnesium in their blood also have higher testosterone levels.
And what about vitamin K2? It also makes bones stronger – and in a Japanese animal study it also boosts the testosterone level.
Int J Endocrinol. 2013;2013:182753.
More vitamin K2, more testosterone 08.11.2011
More magnesium means more testosterone and IGF-1 06.08.2011
High vitamin D level = high testosterone level 01.02.2010