The role of parathyroids for the adaptation to a low calcium intake.

One-year-old selectively parathyroidectomized rats were found to have lost the ability to adapt themselves to a reduced calcium intake. Of importance in this respect was certainly the demonstrated inability to mobilize skeletal calcium to the blood. Thus, when the normal intake of calcium in the diet is reduced in the adult intact rat, skeletal calcium reserves must become mobilized with resulting osteoporosis. Histological and morphometric analyses of the adrenal glands showed no apparent effect of the parathyroidectomy upon the functional state of the adrenal cortex.