Large numbers of people living in the U.S. suffer from osteoporosis, or low bone density, and many aren’t aware of it.

There are treatments, as well as changes in diet and exercise that can help prevent or slow osteoporosis, but no cure exists. A treatment may come soon, thanks to a study that found that bone mass can be increased significantly.

We tend to think of bones as hard structural elements, but we often forget they’re living, growing tissues. Bones consist mainly of collagen, a protein that forms a soft framework, and calcium phosphate, which strengthens and hardens the framework.

Bone is constantly being resorbed, and new bone is formed. When we’re young, bone grows faster than it resorbs, and our bones become longer and denser. Most people reach peak bone density around age 30, after which bone growth slows and bone density declines, sometimes leading to osteoporosis.

There are about 10 million Americans aged 50 years or more with osteoporosis, and another 44 million with low bone density. Women are more likely to suffer bone loss with age. Half of all women, and up to 1 in 4 men, will break a bone in their lifetimes due to osteoporosis.

Scientists were interested in how estrogen affects the body at different stages of life. The hormone estrogen is commonly known to play a role in sexual and reproductive development in women, but it also affects many other systems, including the heart, bones, hair and the brain.

The role of estrogen in the brain isn’t well understood. A part of the brain called the hypothalamus senses estrogen and other hormones, which it uses to regulate essential bodily functions.

When the scientists blocked the sensors for estrogen on nerve cells in the hypothalamus of mice, the mice gained weight and grew less active. The scientists were surprised to find out that the extra weight wasn’t due to extra fat or muscle tissue, but increased bone mass. The bones increased in mass by a whopping 800 percent, and they were extraordinarily strong.

Follow-up experiments focused on a region of the hypothalamus called the arcuate nucleus. Scientists removed estrogen receptors in the arcuate nucleus to cause bone growth, and these mice maintained their bone density through old age.

Astonishingly, this only happened in female mice and not in male mice. When they did the same experiment in mice that develop osteoporosis, mice that had lost 70 percent of their bone mass recovered most of it when the estrogen receptors in the arcuate nucleus were blocked.

The scientists think that after puberty, female brains reassign resources from growing bone to other functions such as reproduction, which leaves women more likely to lose bone density during aging.

We didn’t previously know much about the connection between the brain and the bones, and this could lead to new treatments. This is an exciting new development that furthers our understanding of bone loss in women.

Medical Discovery News is hosted by professors Norbert Herzog at Quinnipiac University, and David Niesel of the University of Texas Medical Branch. Learn more at

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