Quantitative relationship of osteoclasts to parathyroid function
Toft, Robert Jens
Doctor of Philosophy
Over the last decade the tempo of research on the parathyroid gland and its relationship to metabolism has increased rapidly. As new advances in our knowledge of calcium and phosphorus metabolism are made, old ideas and theories must be re-evaluated and some modified, others discarded. New concepts of parathyroid function are being brought forth from the mass of literature which is accumulating. A reversal of thought is taking place regarding both the primary site of action of the parathyroid hormone and the mechanism of control of its secretion. For years it was stated that the primary action of the hormone was to regulate the kidney threshold for phosphorus excretion. In keeping with this idea, it was also felt that the phosphate level of the serum was the direct controlling agent of parathyroid hormone secretion. Enough evidence has now accumulated to show that the primary action of the parathyroid hormone is probably on bone rather than on the kidney. In addition, it is now widely accepted that the serum calcium level controls the secretion of the hormone. To date there has been a general lack of evidence for the exclusive control of hormone secretion by calcium. This is due, in large measure, to the lack of an adequate index of endogenous parathyroid activity. It has been heretofore difficult, if not impossible, to adequately assess the degree of parathyroid secretion under a number of physiological conditions. It is hoped that the work presented herein will prove helpful in providing additional evidence in support of the latter proposition.