Background: Subclinical hypercortisolism is a secondary cause of hypertension that had never been evaluated in resistant hypertensive patients, a subgroup of general hypertensive individuals with an expected high prevalence of secondary hypertension.
Methods: Four hundred and twenty-three patients with resistant hypertension and ages up to 80 years were screened for the presence of subclinical hypercortisolism by morning serum cortisol after a midnight 1 mg dexamethasone suppression test (DST). Those with morning cortisol of at least 50 nmol/l had hypercortisolism confirmed by two salivary cortisol of at least 3.6 nmol/l collected at 2300 h. Statistical analysis included bivariate tests between those with positive and negative screening test and with and without confirmed hypercortisolism, and logistic regressions to assess their independent correlates.
Results: One hundred and twelve patients (prevalence 26.5%, 95% confidence interval 22.0-31.9%) had the screening test positive for suspected hypercortisolism. None had overt Cushing syndrome. Patients with positive screening were older, more frequently males, had higher prevalences of diabetes and target-organ damage and higher nighttime SBPs than patients with normal screening test results. Thirty-four patients (total prevalence 8.0%, 95% confidence interval: 5.7-11.2%) had confirmed hypercortisolism. Independent correlates of a positive DST were older age (P = 0.007), male sex (P = 0.012) and presence of cardiovascular diseases (P = 0.002) and chronic kidney disease (P = 0.016). Correlates of confirmed subclinical hypercortisolism were older age (P = 0.020), diabetes (P = 0.06) and a nondipping pattern on ambulatory blood pressure monitoring (P = 0.04).
Conclusion: Patients with resistant hypertension had a relatively high prevalence of subclinical hypercortisolism, and its presence is associated with several markers of worse cardiovascular prognosis.