Changes in the circadian rhythm of blood pressure in primary aldosteronism in response to dietary sodium restriction and adrenalectomy.

OBJECTIVE: Recently, we found that sodium restriction restored the circadian rhythm of blood pressure from non-dippers to dippers in patients with a sodium-sensitive type of essential hypertension. In the present study, we investigated the effects of sodium restriction on the circadian blood pressure rhythm in patients with primary aldosteronism, a typical sodium-sensitive form of secondary hypertension. DESIGN AND METHODS: We performed 24 h blood pressure monitoring in eight patients with primary aldosteronism due to unilateral adenoma (Conn's syndrome) during normal-sodium (7-12 g/day of NaCl) and low-sodium (1-3 g/day) diets, and after adrenalectomy.
RESULTS: Sodium restriction lowered the 24 h mean arterial pressure from 116+/-14 to 109+/-12 mmHg (P< 0.01). During a normal-sodium diet, there was no change in systolic, diastolic and mean arterial pressures during the night-time compared with the daytime. In contrast, during a low-sodium diet, all night-time pressure values were significantly lower than those in the daytime. After adrenalectomy, the night-time pressures in patients on a normal-sodium diet were lower than those of the daytime. The nocturnal mean arterial pressure fall was increased by sodium restriction and adrenalectomy.
CONCLUSIONS: These results indicate that the circadian rhythm of blood pressure was disturbed in patients with primary aldosteronism who maintained a relatively high sodium intake. Both adrenalectomy and sodium restriction restored a nocturnal dip in blood pressure in primary aldosteronism. Therefore, sodium restriction affects the circadian blood pressure rhythm in sodium-sensitive types of hypertension, not only in primary hypertension, but also in secondary hypertension.