In the course of studies on the effect of phytates on calcium uptake in man (1) it became necessary to determine the extent to which endogenous calcium in the feces might contribute to the calcium balance. Although this point has been studied by several investigators (2-5), there is considerable disagreement on the significance of the fecal route for calcium excretion in man. Thus Malm (6) has observed that different individuals may exhibit pronounced variations in the fecal calcium excretion and has suggested that extended observations be made on each proposed test subject. Since this approach is not practical-in many cases, it seemed desirable to establish the significance of the endogenous calcium output in the feces under our experimental conditions.5The method chosen for investigation was to inject radiocalcium (Ca45) intravenously and to de-termine its concentration in the serum, urine and feces during several days. Such carried out in animals (7-10), but few such data are available for man (11-13).
MATERIAL, DESIGN AND METHODSSubjects. Nine adolescent boys, institutionalized for mental inadequacy, but otherwise normal,6 served in the first study (Experiments A and B). In a later experiment (Experiment C), one individual (No. 57) was selected for intensive study. He was a spastic, but neither clinical nor laboratory examinations revealed any abnormalities in his mineral metabolism. The boys ranged in age from 10.9 to 15.7 years, with mean and median ages of 12.6 years. Their height ranged from 124 to 160 cm. with mean and median heights of 142 cm. Their weight ranged from 29.8 to 44.5 kgm., with a mean weight of 35.6 kgm., and a median weight of 36.0 kgm. The mental age of the boys averaged 7.2 years, (median: 7.2 years) and ranged from 5.8 to 9.2 years.The young male adult in Experiment C was 21 years old, weighed 51.4 kgm. and had a mental age of 10.0 years.Design. The subjects (Experiments A and B) were divided into two groups. One group (I.V.) was given the Cae intravenously, while the other group (P.O.) received Cae by mouth. One month later, the P.O. group received the intravenous injection, while the I.V. group received the isotope orally.7 This was done to minimize the effect of periodic or seasonal variations (6,14) and to use each individual as his own control. Preliminary tests had shown that one month after the administration of 0.7 /Ac Cae, the level of Ca' in the blood and in the excreta was no longer measurable. Two years later (Experiment C), one individual was studied intensively 6All of the subjects were under medical care and observation during their usually indefinite institutionalization. They were selected on the basis of clinical examination. Roentgenographs of the chest, knees, hands, skull and spine of six subjects (Nos. 10,11,13,14,15,16) were evaluated by an experienced roentgenologist, who concluded that they did not deviate from the normal range with respect to calcification.7The results on the study with ingested Ca will be presented elsewhere. Methods of analysis for Ca' an...
