Hypertension and hyperparathyroidism. Inverse relation of serum phosphate level and blood pressure.

In a retrospective study of 120 patients with surgically proved primary hyperparathyroidism, 71 patients who were normotensive and 49 patients (41 percent) who were either hypertensive at the time of parathyroidectomy or had a history of hypertension were compared. The mean serum calcium levels in the normotensive and hypertensive patients were very similar (11.6 +/- 0.1 [SEM] mg/dl, and 11.8 +/- 0.1), ruling against the hypothesis that hypercalcemia per se is the dominant cause of the hypertension of hyperparathyroidism. The mean serum creatinine levels in the two groups were also very similar (1.02 +/- 0.05 and 1.09 +/- 0.05 mg/dl), indicating that the hypertension of hyperparathyroidism is not the consequence of advanced renal parenchymal damage. The hypertensive patients did not have a significantly higher prevalence of urolithiasis. A review of the data in this and related studies leads to the conclusion that the hypertension of hyperparathyroidism is heterogeneous in origin. The mean serum phosphate level in the hypertensive patients was significantly lower than that in the normotensive patients (2.20 +/- 0.06 mg/dl versus 2.69 +/- 0.09 mg/dl, p less than 0.02), which may be due to a decrease in renal tubular phosphate reabsorption secondary to hypertension.