Primary hyperparathyroidism and hypertension: persistently abnormal pressor sensitivity in normotensive patients...

To examine the effects of primary hyperparathyroidism separately from those of hypertension per se on blood pressure regulation in patients with primary hyperparathyroidism, we studied the pressor response to infused angiotensin II (AII) and to norepinephrine (NE) in 7 normotensive patients with primary hyperparathyroidism before and after surgical cure, and compared it to that observed in 10 subjects with idiopathic hypertension and 10 normal controls. While the subjects were on an ad libitum diet, we measured urinary and plasma electrolytes, creatinine, and plasma renin activity. Except for calcium, these values were not significantly different among the three groups. The blood pressure was measured basally and in response to graded doses of AII or of NE until a 20-mmHg increase in the diastolic blood pressure was reached ("pressor dose"). The pressor doses of AII and of NE were lower in the normotensive patients with primary hyperparathyroidism than in normal controls [4.6 +/- 2.0 vs. 7.3 +/- 3.5 ng/kg/min (p < 0.05) and 164 +/- 114 vs. 302 +/- 176 ng/kg/min (p < 0.05) respectively] and not significantly different from those found in idiopathic hypertension (3.1 +/- 1.2 and 137 +/- 95 ng/kg/min). When the patients with primary hyperparathyroidism were studied again between 2-6 months after surgical cure, their pressor doses of AII and of NE remained unchanged from their preoperative values (5.4 +/- 2.9 and 137 +/- 80 mg/kg/min). We conclude that the hyperparathyroid condition can disrupt the normal responsiveness to pressor agents even if the blood pressure remains within normal limits, and that this abnormality may persist after surgical cure.