Serum cortisol in the white-coat phenomenon

Background: The rise in blood pressure associated with a clinic visit (the white-coat phenomenon) may result from anxiety or an alerting reaction. There is evidence to suggest that glucocorticoids may be involved in the mechanism of stress-related blood pressure elevation, but the relationship between the white-coat phenomenon and glucocorticoids has not been assessed. Design: Forty-eight young subjects with essential hypertension were compared with 12 control normotensive subjects. Methods: Home blood pressure monitoring for 7 days and serum cortisol at 0900 h and 2 h rest at 1100 h were measured. The white-coat phenomenon was calculated for systolic and diastolic blood pressures as the difference between clinic blood pressure and average home blood pressure. Results: The serum cortisol level was significantly greater at 0900 h than that at 1100 h in the hypertensive subjects and was higher in the hypertensive subjects than in the normotensive subjects (21.5 ± 0.5 versus 14.3 ± 0.9 mu;g/dl), but there was no difference between serum cortisol levels at 1100 h in the two groups. The magnitude of the white-coat phenomenon, which was greater in the hypertensive subjects than in the normotensive group (22 ± 2/12 ± 1 versus 4 ± 3/1 ± 3 mmHg), correlated with serum cortisol at 0900 h, but not at 1100 h. The higher level of serum cortisol at 0900 h was confirmed by another measurement conducted 4 months later in a subsample of the hypertensive subjects (n = 18). Conclusions: These results suggests that the white-coat phenomenon is related to the transient increase in serum cortisol or psychological stress, or both, which can trigger arousal of the hypothalamic pituitary adrenocortical axis.