Fig. 4.

Relationship between distal calcium reabsorption, renal calcium excretion, and distal calcium delivery. Symbols as in Fig. 1. Distal calcium reabsorption (top left) rises with calcium delivery in normal subjects and IHSF patients. Values for both lie beneath the uppermost diagonal line of identity. Many IHSF reabsorption values lie beneath normal at overlapping values of distal calcium delivery, indicating a reduced fractional reabsorption of distally delivered calcium. The actual fraction (%) of distally delivered calcium excreted (top right) fell with increasing distal delivery, and points from many IHSF patients lie above normal points at comparable distal delivery; this panel visually amplifies the findings of panel at top left. Fractional and total calcium excretions, likewise, were high in many IHSF patients vs. normal subjects at comparable deliveries (bottom). Statistical analyses are in Tables 3 and 4.