Think your bones stopped growing by the time you finished high school? Think
again. Bones constantly remodel themselves throughout life, growing here,
In osteoporosis, though, normal bone remodeling goes awry. Bone loss exceeds
bone growth, and bones become thin and weak. Osteoporosis affects 10 million
Americans, leading to 1.5 million fractures every year.
Osteoporosis medications and physical activity can tip the balance of bone
remodeling, preserving bone strength. How does bone remodeling work? What can
be done to slow down or reverse bone loss? Read on to learn what you can do to
keep your bones healthy and strong.
Bone Remodeling: A Never-Ending Improvement Project
"People think bones are static, but in fact bone is constantly growing
and being resorbed," says Mary Zoe Baker, MD, an endocrinologist and
professor of medicine at the University of Oklahoma Health Sciences Center in
Oklahoma City. "It has to, in order to heal damage and microfractures"
that occur with normal wear and tear, says Baker.
The process of bone remodeling is a give-and-take between two opposing
forces, replacing old bone with new bone.
Bone loss (resorption): Special cells called osteoclasts break down
bone. They are like a demolition crew. When the signal comes, osteoclasts are
recruited to enter the bones and secrete enzymes that break down collagen and
minerals. Somehow, they know just when to stop to avoid damaging the
Bone growth:Special cells called osteoblasts line the surface of
bones. In response to signals in the blood, the osteoblasts get to work. They
lay down bone, by depositing calcium and phosphate crystals on a scaffolding of
In healthy bone, the processes of growth and resorption are equalized.
Various hormones, including estrogen in women, help keep this balance.