256 



G. F. Mazzuoli, L. Terrenato 



calcium intake and output are equal and balance reaches the equilibrium. Fig. 1 also 

 shows the mean calcium requirement of normal subjects on the basis of data collected 

 from the literature and analyzed by Nordin (1962). The data indicate that calcium 

 metabolism in acromegaly differs from that of normal subjects in two respects. In the 

 first place, the calculated mean requirement is significantly greater. Secondly, the 

 regression of output on intake is less steep than in normal subjects, so that both the 

 negative balance in patients on low calcium diets, and the positive balance in those 

 on high calcium diets, are greater than normal. 



Fig. 2 shows the regression line of fecal calcium on calcium intake found in acro- 

 megalic patients and the regression line of the two parameters in normal subjects as 

 reported by Nordin (1962). The figure also shows the values of urinary calcium 

 excretion on calcium intake of acromegalics and the regression line found in normals 

 by Nordin (1962). At all intake levels, urinary calcium of acromegalic patients is 

 higher and this contributes to their higher calcium requirement. On the other hand 



Observalions from lileralure 

 Personal Observalions 



^ y 



500 /OOO /JOO 500 lOOO 



Calcium inloke mg/day 



elatlonship between calcium intake and fecal and urinary calcium 

 in acromegaly 



/soo 



normal subjects and 



urinary calcium seems to be less influenced by calcium intake. In fact the correlation 

 between urinary and dietary calcium is very low and the regression line of fecal 

 calcium on intake is parallel to that of total calcium output on calcium intake. 



The regression line of fecal calcium on intake is less steep than in normal subjects. 

 Extrapolating this line to the theoretical intake of zero, the fecal calcium of acro- 

 megalic patients appears to be higher than in normals, suggesting a higher excretion 

 of endogenous fecal calcium. This finding has been confirmed by radiocalcium data, 

 the endogenous fecal calcium excretion ranging between 180 and 250 mg/day in five 

 out of six patients studied. On the other hand, the slope of regression of fecal calcium 

 on intake suggests that the percent absorbed decreases on low calcium diets and 

 increases on high calcium intakes. It seems therefore, that in acromegaly the higher 

 values of both the negative and positive calcium balances, at respectively low or high 

 calcium intakes, are due to both the urinary and fecal calcium excretion. 



The percentage of radiocalcium absorbed in acromegalics ranged between 24 to 

 71^/o of the administered dose. Wide ranges have also been observed by many authors 



