We monitored the circadian profile of cortisol, systolic and diastolic blood pressure (SBP and DBP), heart rate (HR) in 33 normotensive subjects aged 20-40 years, 20 normotensive subjects aged 40-60, 32 patients with essential hypertension and 13 patients with Cushing's syndrome (6 pituitary adenomas, 5 adrenal adenomas and 2 adrenal carcinomas). All controls and patients underwent serial blood drawings at 4-h intervals during the 24-h cycle. BP and HR were recorded every 30 min by an automatic, room-restricted instrument. Data were analyzed by conventional statistics and by chronobiological procedures (cosinor rhythmometry) to quantify rhythm parameters such as the MESOR (rhythm-adjusted average), amplitude (difference between maximum and MESOR) and acrophase (timing of the crest of the rhythm). Both the control and essential hypertensive subjects showed a BP and HR circadian profile characterized by a peak in the early afternoon and a clear nocturnal fall (rhythm detection: p less than 0.001). The chronobiological analysis did not reveal any significant difference between healthy young and aged subjects. BP rhythmicity was disrupted in patients affected by Cushing's syndrome, whereas the 24-h oscillation of HR was preserved (p less than 0.001). Patients with pituitary-dependent Cushing's syndrome had higher BP levels than adrenal-dependent subjects (p less than 0.001). Our data are compatible with the view that glucocorticoids are involved in the control of BP circadian rhythm, whereas HR is not under their control.
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