THE RELATION OF THE PARATHYROID HORMONE TO THE STATE OF CALCIUM IN THE BLOOD

Abstract

The state of Ca in the serum in conditions approximating hypo- and hyper-function of the parathyroid glands was studied, chiefly in cats; a few observations upon chronic latent tetany in the dog are included. The changes found were simply the quantitative changes predicted by the mass-law relationship between Ca and protein, previously described, there being no evidence of a qualitative change in the state of Ca. Parathyroid tetany, in the cat, was observed only when the Ca++ concentration fell below 0.65 mM per kilo H2O, and then only irregularly. Chronic latent tetany, in the dog, was accompanied by a chronic lowering of the Ca++ concn. in the plasma. It is concluded that a regulatory mechanism, in which the parathyroid hormone plays a decisive part, functions so as to maintain the Ca++ concn. of the plasma at a physiological level. Parathyroidectomy leads to a reduction in the Ca++ level, administration of parathyroid hormone to an increase.