MadSci Network: Biochemistry
Query:

Re: calcium and osteoporosis

Date: Wed Jul 22 12:15:48 1998
Posted By: Leslie Gartner, Faculty Histology/Anatomy, University of Maryland, Baltimore, MD
Area of science: Biochemistry
ID: 900816357.Bc
Message:

Dear Nancy,

Your confusion between the experiment that you performed, that is, 
decalcifying a chicken bone and the brittleness of bone in an individual 
who is suffering from osteoporosis is understandable. Unfortunately when 
people talk about osteoporosis, they concentrate on just calcium rather 
than the actual problem.
When you placed the chicken bone in vinegar and removed calcium you 
simulated a condition known as "osteomalacia," where not enough calcium is 
deposited in the forming bone (in kids the same condition is known as 
"rickets," it is only in adults that it is called osteomalacia). People 
suffering from osteomalacia have bones that do not have enough calcium in 
them and the bones begin to bend, especially the long bones of the leg, 
under the weight of the body. 
Individuals who have osteoporosis have a different problem, namely, they 
lose bone tissue, not just calcium. Technically, their bones do not become 
more brittle. Instead they have thinner bones than they should for their 
body mass and thus they are more likely to break. However, if you take a 
piece of osteoporotic bone and a piece of normal bone, the bone composition 
(% of inorganic substances and % of organic substances) will be the same as 
for normal bone. However, for the same volume of bone tissue, the bone mass 
will be less. What I am trying to say is this: assume that you take one of 
the vertebrae from the individual before osteoporosis sets in and weigh 
that vertebra and measure its density. Then put it back in where you found 
it and wait a few decades until after osteoporosis has set in. Then take 
out the same vertebra, you'll find that now it weighs less and has less 
density. But, biochemically its composition will not have changed.

I hope this helps.

Les Gartner, Ph.D.
Department of Anatomy,
Dental School
University of Maryland at Baltimore
lgartner@umaryland.edu



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