Patients with primary aldosteronism, which is the most prevalent form of secondary hypertension, have an increased rate of cardiovascular events, compared to patients with essential hypertension, even with equal severity of hypertension. This might be partially attributed to the association of increased aldosterone levels with insulin resistance. How this relation can be explained from a pathophysiological point of view, is insufficiently established.

Recently, microvascular dysfunction has been proposed as a link between insulin resistance and hypertension. Loss of NO-mediated vasodilation is an important feature of microvascular dysfunction; in addition, an impaired insulin-mediated microvascular NO production has been suggested to underlie the reduction in insulin-stimulated glucose disposal that is characteristic of insulin-resistant states. Increased aldosterone levels are not only associated with insulin resistance, but also with endothelial dysfunction. In addition, they interfere with the vascular effects of insulin.

Therefore, the investigators hypothesize that in patients with primary aldosteronism, increased aldosterone levels induce microvascular dysfunction through reduction of NO-availability, which contributes to the development of insulin resistance, and of hypertension, in addition to the sodium-retaining effects of aldosterone.

Inclusion Criteria:

Patients with primary aldosteronism

• Age 18-70 years
• Confirmed diagnosis of primary aldosteronism
• Serum potassium > 3.5 mmol/L with or without supplementation

Patients with essential hypertension

• Age 18-70 years
• Secondary causes of hypertension excluded

Exclusion Criteria:

• Cardiovascular disease (stroke, coronary artery disease, peripheral vascular disease, congestive heart failure, cardiac shunts, cardiac surgery, pulmonary hypertension, cardiac arrhythmias, family history of cardiac arrhythmias or sudden cardiac death)
• Diabetes mellitus
• Unstable or severe pulmonary disease
• Inflammatory diseases
• Alcohol use > 2 U/day (women) / > 3 U/day (men)
• (Frequent) use of acetylsalicylic acid, NSAID's, dipyridamole and corticosteroids
• eGFR < 60 mL/min
• Impairment of hepatic function
• Pregnancy or lactation

Twenty patients with primary aldosteronism and twenty patients with essential hypertension