Parathyroid hormone and calcium. A relationship in hypertension.

Total and ionized calcium, parathyroid hormone, calcitonin, and renin activity were measured in 27 untreated patients with essential hypertension. There was no relationship between any of these parameters and diastolic blood pressure. However, a significant inverse relationship was found between diastolic blood pressure and the ratio of either total or ionized calcium to parathyroid hormone (r = -0.40, P less than 0.05; and r = -0.38, P less than 0.05, respectively). The ratios did not correlate with patient age or plasma renin level. This preliminary finding suggests that the role of plasma calcium in hypertension may need to be analyzed in the context of overall calcium metabolism, as influenced by the parathyroid hormone. The role of an altered relationship between plasma calcium level and parathyroid hormone in the pathophysiology of essential hypertension remains to be studied.