The parathyroid glands, which are structures anatomically located in close relationship to the thyroid gland, have an important function in the calcium-phosphorus metabolism of the body. Partially because of the comparatively recent isolation of their hormone, little is known concerning their true relationship to the other glands of internal secretion of the body. Derangement of their function with resultant hypersecretion, or hyposecretion, is followed by distinct trains of symptoms and changes in body function in which bone lesions and nervous reactions are prominent. In these the derangement of the normal calcium-phosphorus balance is the immediate cause. Specifically the parathyroid hormone increases the serum calcium level and will mobilize calcium from any body tissue where it is available.

Certain workers believe that parathyroid function can be entirely supplanted by the use of vitamin D and proper diet. This theory has not been definitely proved, and there is reason to doubt that it is true. Clinically, it is true that symptoms of hypoparathyroidism usually can be relieved by administration of vitamin D and proper diet.

Indiscriminate calcium therapy may be and often is dangerous to the patient. Hypercalcemia does not necessarily mean that adequate calcium is being supplied to the tissues. Actually it may be on the way out, and demineralization of the body may be taking place.