Intestinal Absorption and Skeletal Dynamic of Calcium in Acromegaly 



255 



12 to 24 days) included kinetic study periods (lasting 8 to 12 days). Four patients 

 were given ^^Ca orally as well as intravenously. Two patients received only ■^^Ca 

 orally. Urine and stools were collected daily. Stools were separated at intervals of 

 four days with carmine markers. Feces and food were homogenized and converted to 

 ash before analysis. Daily determinations of -^^Ca were made on samples of plasma, 

 urine, and stools. 



After intravenous ■^^Ca administration, calcium pool and bone accretion rate were 

 determined according to the equation of Bauer et al. (1957): Bt = ESt + Aj'^S(t) dt='"; 

 endogenous fecal calcium according to the equation of Blau et al. (1954): Endogenous 



fecal Ca = „■ ■ X total stool calcium; bone resorption by subtracting calcium 



S. A. serum 

 balance from accretion rate. Calcium intestinal absorption was calculated by the 

 following relationship: Dietary calcium absorbed = dietary calcium — (total fecal 

 calcium — endogenous fecal calcium). 



After oral ^^Ca administration the percentage of absorption was calculated by 

 subtracting from the total radiocalcium excretion recovered the amount of radio- 

 calcium excreted during the intravenous study. In two patients, who received only 

 the oral dose, it was calculated by extrapolating to zero the S.A. of stool following 

 the excretion of the unabsorbed portion of the dose. 



Results and discussion 



Fig. 1 shows the results of our balance studies and also data collected from the 

 literature. A high correlation exists between calcium intake and output, calcium 

 balance becoming increasingly positive as calcium intake rises. The figure also shows 

 the regression line of calcium output (y) on calcium intake (x) and the 95 per cent 

 confidence limits. The point at which the mean regression line intercepts the 45 degree 

 line corresponds to the mean calcium requirement, that is, the mean value at which 



, ..„ , \ \ J ^Normal- y=0. 73Sx->-l6ltm 



'^""^ ~ ~ ^ ^ " ' "' ^ r- 0.37 (p ^0.01) 



'4cromego/y:0. '/SSx-f- S33i202 

 r = 0.63 (p< 0.01} 



o Observafions from liferature 

 • Personal observations 



1500 2000 



Calcium intake mg/day 



Norma/ Acromegaly 

 Mean requirement 



;romegaly (6 personal 



Fig. 1. The regression of calcium output on calcium intake in normal subjects and 

 21 cases collected from literature) 

 * Where: Bt = Amount of isotope retained in the body at time t. E = Amount of exchangeable calcium. 

 A = Rate of calcium accretion. St = Serum specific activity at time t. Iq S(t) dt = Integrated specific activity. 



