Pure calcium deficiency produces osteoporosis, or bone atrophy, in rats, while vitamin D
deficiency as well as calcium deficiency leads to osteomalacia, or thin bones with wide
osteoid seams. The retention of a dose of strontium in the osteoporotic rats is greater than
normal, and this indicates rapid bone formation. The immediate cause of the bone thinning
must therefore be an increase in the rate of bone resorption, contrary to the classical
concepts of osteoporosis.