Abstract
In the study of experimental hypoparathyroidism 2 factors frequently cause contradiction and confusion: (1) the anatomical relation of the parathyroid in the animals employed; and (2) the composition of the diet, especially with respect to its calcium and phosphorus content. In experiments with the dog or the monkey the extirpation of the parathyroids without destruction of thyroid tissue is frequently impossible and the complete operation of thyroparathyroidectomy must be used. That the thyroid alone has a profound influence on calcium and phosphorus metabolism has long been appreciated and recently Aub 1 and his associates have demonstrated this fact by metabolism experiments in human beings. Hence the removal of the thyroid along with the parathyroids may cause an alteration in calcium and phosphorus metabolism different from that observed when either of them alone is removed. The rat, on the other hand, has but 2 encapsulated and easily removable parathyroids. Erdheim 2 and his followers made use of this anatomical fact and produced tetany in rats by cauterizing the parathyroids, and causing little or no destruction of the adjacent thyroid tissue. Erdheim showed that parathyroidectomy in the rat produces faulty dentition, delays calcification of a callus and impoverishes the body of lime salts.
The experiments of Erdheim were conducted prior to our more exact knowledge of complete diets and hence no control of calcium and phosphorus intake was considered. Even in recent times the diets used in experiments on dogs and monkeys have consisted mostly of meat and biscuit and hence have been of a high phosphorus and low calcium variety. The addition of milk to such a diet or the accidental finding of calcium in infusorial earth used in metabolism experiments is looked upon by many as a faulty procedure; and milk is frequently referred to as having detoxifying properties in relieving parathyroid tetany.
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