Studies of acute experimental parathyroid insufficiency. I. Blood plasma levels of calcium and inorganic phosphorus in the various forms of insufficiency

Abstract

In 37 dogs we have analysed in the plasma the calcium content (average 10’5 mg. per cent; <r = 1’5) and the inorganic phosphorus content (4’2 mg. per cent; <r = 1’0). In normal dogs there is some proporcionality between the plasmatic valúes of Ca and P : In 13 dogs with P 4 mg., P = 38 % of Ca ; in 15 dogs with P = 4 mg., P = 43 % of Ca ; in 11 dogs of other group P = 44 % of Ca. As seen the percentage is about the same. The percentage of P in ,the hydro- xiapatite, which is the principal salt' in the bones, is 46 % of Ca.

The parathyroid glands were removed in 33 dogs, and we had 28 cases of tetany (16 convulsive tetany ; 4 hipertonicity without convulsions ; 3 respiratory disturbances only ; 2 hemorrhagic diarrhoea, and 3 hypotonicity with great asthenia). Often in the convulsive form we found before hypertonicity a stage with hypotonicity and ataxia. Our dogs all died on account of tetany but two which cure spontaneously and other three which cure by administrations of calcium and vitamin C or A T 10.

The disminution of the Ca content of the blood was present in all our cases of tetany. It falls to 41-57 % of the normal figure. The rise in the inorganic P content of the plasma is not present in all the cases of tetany: There is no rise in hipertonicity without convulsions, nor in asthenic form of tetany. But other cases have a steady rise in the P content: Kespiratory 50 %, digestive 80 % and convulsive 93 % more thaii the normal figure of each dog: in convulsive tetany from 0 to 27 %.

In tetany owed to parathyroid insuffideney the diminutions of the Ca content of the blood is constant and uniform, but the in­ crease of the inorganic phosphorus is not constant and has great variability. Therefore it is not possible to consider the phosphorus disturbance as the basic and primary phenomenon of parathyroid insufficiency ftom which Ca disturbance would be just a consequence. Ca alterations must be essential and it is the cause of P increase. But also it is possible the exístencc of an unknown factor as determinant of botn disturbances. The rise up of P in the blood, the diminutions of Ca in the blood or the relation slup between Ca and P are not the cause of tetanicconvulsions.

In convulsive tetany we found very often great increase of P. As explanation we think as follows : Owing to the strong and lasting muscular contractions of the animals a great quantity of inorganic I’ pass to the blood from which the kidney is not able to remove it on account of defficient power to phosphate elimination.

Death by convulsivo tetany — and even more in other forms — is not caused by a determined disturbance of Ca or P in the blood.