258 Mazzuoli, Terrenato: Intestinal Absorption and Skeletal Dynamic of Calciur 



urinary calcium excretion and its inverse relationship to the amount of calcium ab- 

 sorbed, remain to be explained. 



y 



800 





Normal ^ x= 1.85 y+ 207 



= Persona/ obser- 

 vofions in ocrome- 



I goiy 



2000 3000 WOO 



Bone formation mg/day 



5000 



Fig. 4. The relationship betwe 



ilcium absorption and bone formation in acromegalic patients and in nor 

 teoporotic subjects as reported by Biuinner et al. 



2. The growth hormone affects primarily the bone resorption: the equilibrium of 

 the balance would depend on the ability of bone formation to adapt to the rate of 

 bone resorption. This interpretation would provide a more adequate explanation for 

 both metabolic and skeletal dynamic changes observed in acromegaly. 



In conclusion our findings in acromegalic patients indicate that: 



1. The mean calcium requirement is increased due to both higher urinary and 

 endogenous fecal calcium excretion. 



2. Bone turnover is increased but the balance is never as positive as would be 

 expected by the high values of bone formation rate. This suggests that the abnormality 

 of skeletal metabolism may be due to a primary action of growth hormone on bone 

 resorption. 



3. The intestinal absorption of calcium may be normal or even high, but it is 

 always inadequate for the bone accretion rate. 



Acknowledgement 

 The authors are indebted to Miss Antonella Scarda for her invaluable technical 



assistance. 



References 



Bauer, G. C. H., A. Carlsson, and B. Lindquist: Bone salt metabolism in humans studied 

 by means of radiocalcium. Acta med. scand. 158, 143 (1957). 



Blau, M., H. Spencer, J. Swernov, and D. Laszlo: Utilization and intestinal excretion of 

 calcium in man. Science 120, 1029 (1954). 



Bronner, F., R. S. Harris, C. J. Maletskos, and C. E. Benda: Studies in calcium meta- 

 bolism. J. Nutr. 59, 393 (1956). 



— , L. J. RiCHELLE, P. D. Saville, J. A. Nicholas, and J. R. Cobb: Quantitation of calcium 

 metabolism in postmenopausal osteoporosis and in scoliosis. J. clin. Invest. 42, 898 (1963). 



Grazia, J. A. DE, and C. Rich: Studies of intestinal absorption of Ca45 in man. Meta- 

 bolism 13, 650 (1964). 



NoRDiN, B. E. C.: Calcium balance and calcium requirement in spinal osteoporosis. Amer. 

 J. clin. Nutr. 10, 384 (1962). 



The references concerning the metabolic balance data collected from literature have been 

 omitted for space requirement. 



