76 



J. C. BiRKENHAGER, J. VAN DER SlUYS VeER, R. O. VAN DER HeUL, D. SmEENK 



It has been shown in different cases of Cushing's syndrome but with the same 

 degree of osteoporosis that osteoblastic activity and tetracycline uptake may vary 

 from subnormal to higher than normal (van der Heul et ai, 1964). This suggests 



PHOSPHORUS/ HYDROXYPROLINE 

 RATIO 



HYPERPARATHYROII 

 M GUSHING 

 HYPERTHYROIDISM 

 CONTROLS 



= -0.0154) 



= -27 09 y 



+ 3.38 



+ 1055 

 P < 0.001 



% TETRACYCLINE LABELLED SURFACE 



Fig. 3. Correlation between the phosphorus-hydroxyproline ratio and percentage tetracycline labelled bone sur- 

 face in iliac crest bone 



that in this condition bone disease is initiated by an increase of bone resorption. This 

 view is supported by the finding of a normal (Sissons, 1956) or sometimes increased 

 (van der Heul ct ai, 1964) osteoclasis in histologic studies, and of the primary 



catabolic effect of corticoids in 

 kinetic studies with a bone-seeking 



M GUSHING 

 HYPERPARATHYROIDISK 



CONTROLS I tracer (Gordan and Eisenberg, 



1963). 



In Fig. 3 a negative correlation 

 is shown between the percentage 

 tetracycline-labelled bone surface 

 and the P/HP ratio of bone from 

 the groups of patients with hyper- 

 parathyroidism or hyperadreno- 

 corticism, from two patients with 

 hyperthyroidism and from two 

 controls. As the P/HP ratio reflects 

 the average degree of mineraliza- 

 tion it could be expected that bone 

 with a low P/HP ratio contains a 

 relatively large amount of bone 

 with a very low degree of mineralization and consequently will show a high tetra- 

 cycline uptake. The P/HP ratio appears to be independent of age in the three groups 

 studied (hyperparathyroidism, hyperadrenocorticism and control group) as can be 

 seen in Fig. 4. 



Fig 



Phosphor 



■hydrox\p 

 plotted 



■atio 

 age 



AGE YRS 

 ;st hone 



