Essential hypertension, chronobiological study of the circadian variations in urinary excretion of free catecholamines.

: Arterial blood pressure and urinary free catecholamine excretion of 8 hypertensive and 4 normotensive women have been evaluated by 3-h interval samples for 2 consecutive days. After noticing the effects of sleep on the arterial blood pressure and on the daily variation of urinary free catecholamine excretion, the authors examined the possible different role of the adrenergic system in hypertensive subjects.