Bone Formation and Resorption in Bone Disorders 



71 



the result of either exogenous or endogenous hypercortisonism. Resorption was 

 elevated, often considerably, in all but four cases. Formation was reduced in all cases, 

 values in nine cases falling below two standard deviations from the normal. The 

 osteoporosis of hypercortisonism, therefore, differs from idiopathic or senile osteo- 

 porosis in that, as well as the increased resorption which contributes most importantly 

 to the loss of bone, there is a decrease in bone formation. 



Bed-rest 



Immobilization has been shown to result in decreased density of the skeleton 

 (Heaney, 1962); therefore any individuals who had more than four days of bed-rest 

 were excluded from the main part of the study. 



Such individuals fell into two groups, namely "normal" individuals who had no 

 bone disorder and osteoporotic individuals who had been in bed from four to 

 seventeen days. The results of measurements of formation and resorption in fourteen 



Fig. 1. Bone resorption and formation in some disorders of tlie skeletc 



individuals from each of these groups suggested that the result of bed-rest was to 

 depress bone formation. Bone resorption was within normal levels in the group with 

 no bone disease and characteristically elevated in the osteoporotic individuals. 



