new hormone for Testosterone?

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From the magazine " New Scientist "

Low sperm count? Your bones might be to blame

17:42 17 February 2011 by Hamzelou

Sex hormones are already known to play an important role in maintaining healthy

bones – but the relationship may be a two-way street. New evidence suggests that

bones are important for controlling testosterone levels.

Gerard Karsenty at Columbia University in New York City and his colleagues

applied osteoblasts – bone cells involved in building new bone – to cultures of

cells taken from either the testes or ovaries of mice. They found that testis

cells treated with bone cells increased their production of the hormone

testosterone threefold. The cells from the ovaries, on the other hand, showed no

change in their production of the hormones progesterone and oestradiol.

Karsenty's team then focused in closer by looking at osteocalcin – a hormone

produced by osteoblasts. They found that testis cells treated with an active

form of the hormone released testosterone – and the more of the hormone they

got, the more testosterone they produced. Injecting live mice with the hormone

similarly boosted levels of testosterone in their bloodstream.

To find out if this effect on testosterone production might affect mice's

fertility, the team knocked out the gene for osteocalcin in a group of the

rodents. These modified mice had significantly smaller testes and lower sperm

counts than their normal counterparts – and when the group bred them with normal

females, they found that the litter size was around half normal.

Mice and men

Sokol at the University of Southern California in Los Angeles is

intrigued by the findings. " I am particularly surprised by the absence of

effects in female mice, " she says.

Karsenty is stumped too. " We were flabbergasted, " he says. " Don't ask me why it

only affects males because I don't know. "

He thinks the hormone might also boost fertility in men, as many hormones have

been found to have the same effects in mice and humans. His team are currently

exploring the possibility of osteocalcin as a treatment option for infertile

men.

Bone is already known to release hormones. A few years ago, the same group found

that osteocalcin plays a role in maintaining the body's glucose levels (Cell

DOI: 10.1016/j.cell.2007.05.047).

Journal reference: Cell, in press