“ Calcium absorption is significantly reduced in postmenopausal women with vertebral fractures ”
The first reported in 1973 on the basis of calcium balance studies 
And confirmed in 1984, 1991 By using a radiocalcium absorption test [2,3]
“ C alcium absorption is the main determinant of calcium balance ” 
“ T he only peripheral fracture in which this has actually been reported is hip fractur e ” [6,7]
In the present paper,
we show that reduced calcium absorption is associated with several other fractures besides those at the spine and hip but probably not with lower leg fractures .
The 549 women included the following :
172 (control) no fracture
who had not experienced a peripheral fracture from minor trauma and had normal spine radiographs;
72 peripheral only
who had experienced one or more peripheral fractures but also had normal spine radiographs;
147 Spine only
who had one or more wedged or crushed vertebrae but no history of peripheral fracture; and
158 Both (spine+peripheral)
who had one or more fractured vertebrae and a history of peripheral fracture .
height and weight,
radiography of the lateral lumbar and ( breathing ) thoracic spine
other disorders known to affect bone were excluded
Clinical method The subject arrived after overnight fast blood sample was withdrawn. As blank, 1,25-(OH)2 Vit.D3
Give them an oral dose.
5 uCi Ca-45 in 20 mg calcium (in chloride form)
in 250 distrilled water.
Blood sample taken exactly 60 min later. Centrifuge. Count plasma aliquots By liquid scintillation counter
inspection of the data suggested that the absorption deficit in those with vertebral fracture was mainly due to those with two or more fractures
The latter represents an absorption deficit of 29% compared with the no - fracture cases .
Mean ~ 0.7 Mean ~ 0.51 100 % absorption 71 % absorption
All were significantly lower than the controls except fractures of the tibia, foot and, ankle .
The largest and most statistically significant deficits were at the spine, hip, and humerus .
The percentage deficits in radiocalcium absorption ranged 10% - 35%
The most significant relative risks were related to fractures of the humerus, vertebrae, and hip . Calcium absorption was not significantly related to fractures of the ankle, foot, or tibia , but they were also the smallest groups Age was a significant determinant of all fractures except those of the tibia .
We have shown that calcium absorption, adjusted for age and measured with a low - carrier isotope test that almost certainly measures active transport [ 10 ] , is significantly reduced not only in postmenopausal women with vertebral fractures but also in many of those with peripheral fractures .
The mean value in our controls ( i . e . , those with no history of fracture ) was 0.72 / h or virtually the same as the young normal mean of 0.70 / h [ 14 ] ,
and the absorption deficits in the fracture cases ranged from 10% to 35% though not significantly different from each other .
The absorption deficits were not significant in fractures of the tibia, foot, and ankle, but the numbers in these three groups were small and did not have the power to discriminate between them and the controls at 5% significance . Therefore, the possibility remains that calcium absorption is reduced in these groups as well .
What estrogen appears to do is to reduce the resistance to calcitriol caused by estrogen deficiency calcitriol and PTH production in responseto the increase in bone resorption and assumed increase in ionized calcium(hypercalcimia) Calcium absorption is reduced. Machanism for monitor Ca homeostasis secretion of PTH the increase in bone resorption Cause of osteoporosis in postmenopausal women
Radiocalcium absorption test Ca-45 Blood intestine T Low calcium absorption low count rate Bone
We conclude that there is an association between reduced calcium absorption and fractures in postmenopausal women which is probably causal and has important implications for the prevention and treatment of postmenopausal osteoporosis
Impaired calcium absorption
is particularly associated with those fractures for which osteoporosis is