Effects of Parathyroid Deficiency and Calcium and Phosphorus of the Diet on Pregnant Rats

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Abstract
Parathyroid deficiency in the rat is associated with markedly diminished fertility, moderate reduction in the number per litter and a significant reduction in the average birth weight. These effects are more conspicuous on diets either low in calcium or high in phosphorus. Parathyroid deficiency in the pregnant rat is also characterized by prolongation of the gestation period, tetany at term, prolonged labor and high rates of maternal and fetal mortality. These abnormal manifestations appear to be related to the marked lowering in serum calcium. The concentration of inorganic phosphate in the blood serum of operated animals is usually above that of the controls on the same diet. The phosphatase is usually lower than in the controls, indicating that the capacity for cellular activity is less in the bones of the parathyroid-deficient rat than in those of the normal animal. In parathyroid-deficient rats fed a diet abnormally high in calcium and relatively low in phosphorus (diet no. 16 of Cox and Imboden), the values for serum calcium, phosphorus and phosphatase fell within the same limits of variation and showed approximately the same averages as in the normal controls. The abnormal manifestations of late pregnancy were likewise abolished and the differences in per cent fertility, average number per litter and average birth weight were greatly minimized.