The circadian blood pressure rhythm was compared between patients with Cushing’s syndrome and those with essential hypertension or primary aldosteronism. In patients with essential hypertension or primary aldosteronism, clear nocturnal falls in systolic and diastolic blood pressure and the heart rate were observed. In contrast, in patients with Cushing’s syndrome there was no nocturnal fall in blood pressure, and even a rise in some cases. In all cases with Cushing’s syndrome, there was a nocturnal fall in the heart rate. Exogenous glucocorticoid abolished a nocturnal fall of blood pressure in patients with chronic glomerulonephritis or systemic lupus erythematosus, but did not affect nocturnal falls in the heart rate. These results indicate that the normal circadian rhythm of blood pressure may be regulated, at least in part, by the hypothalamo- pituitary-adrenal system.
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