Effect of adrenal suppression with dexamethasone in essential hypertension.

The 24-h integrated plasma concentration of aldosterone (IC-ALDO), PRA (IC-PRA), and cortisol (IC-F) were measured in 34 male patients with uncomplicated mild essential hypertension and 15 matched normal controls using a portable 24-h continuous nonthrombogenic blood withdrawal system. The hypertensive were subsequently given 0.5 mg dexamethasone three times per day, resulting in suppression of their urinary excretion of 17-hydroxycorticosteroids and free cortisol. The diastolic blood pressure of the hypertensives fell during adrenal suppression from 104 +/- 5 to 96 +/- 8 mm Hg (mean +/- 1 SD; P less than 0.0001). The systolic pressure fell from 150 +/- 16 to 148 +/- 17 (P greater than 0.01). Baseline values for IC-F, IC-ALDO, and IC-PRA were similar in hypertensive subjects and normal controls. After treatment with dexamethasone for 8 weeks, IC-F in the hypertensives decreased from 7.8 +/- 2.1 to 0.7 +/- 0.6 microgram/dl (P less than 0.0001). There was no associated change in IC-ALDO or IC-PRA. Thus, the fall in diastolic blood pressure in response to dexamethasone was associated with suppression of IC-F, without demonstrable changes in other endocrine or biochemical factors measured.