THE URINARY PHOSPHATE EXCRETION FACTOR OF PARATHYROID GLAND EXTRACTS: A HORMONE OR AN ARTEFACT?¹

Abstract

TWO hypotheses have been advanced in explanation of the parathyroid hormone control over the level of ionized calcium in the tissue fluids. One is that the hormone induces a release of calcium by a direct stimulating action on the bones (Thomson and Collip, 1932); chemical changes, as reflected by the varying concentrations of calcium and of phosphorus in the serum and in the urine, are considered secondary manifestations. According to the other hypothesis, the hormone acts primarily on the electrolyte equilibria of the body fluids in such a manner as to increase their solvent power for bone salts; bone dissolution follows as a secondary phenomenon (Albright et al., 1929; Albright and Reifenstein, 1948). In brief, the sequence of events is supposedly: (1) the hormone acts on tissue fluid phosphate rendering it more readily excretable by the kidney; (2) serum phosphate is thereby decreased resulting in tissue fluid undersaturation with respect to some equilibrium constant regulating serum calcium and phosphate concentrations;