Recent human studies found tissue sodium storage in patients with hyperaldosteronism that could be detected non-invasively by 23Na-MRI. Tissue sodium accumulation could be mobilized upon treatment of hyperaldosteronism. Besides, former animal studies applying chemical electrolyte analysis indicate that this aldosterone induced sodium storage might be accompanied by intracellular potassium loss. Wether such an intracellular tissue potassium loss occurs in vivo in patients with hyperaldosteronism and if this deficiency can be corrected by treatment is unclear. The investigators will employ 39K-MR Imaging at 7Tesla to further assess this hypothesis.

Patients diagnosed with primary hyperaldosteronism (PA) will be prospetively investigated using 23Na-MRI and 39K-MRI at 7 Tesla to assess tissue sodium and potassium content (prospective observational study). Measurements will be conducted before treatment of hyperaldosteronism and three to four months after adrenal surgery or medical treatment (Spironolactone or Eplerenone). Furthermore, blood pressure, body water distribution (by bioimpedance spectroscopy), pulse wave velocity and serum electrolytes will be assessed.

Additionally, we will conduct a case-control study and compare PA patients before treatment with age- and gender matched healthy control participants. In this study group 23Na-MRI and 39K-MRI at 7 Tesla will be conducted to assess tissue sodium and potassium content using the same MRI protocols as in PA patients. Blood pressure, body water distribution (by bioimpedance spectroscopy), pulse wave velocity and serum electrolytes will be also examined.

Inclusion Criteria for patients with Primary Aldosteronism:

• Primary Aldosteronism diagnosed according to the endocrinological guideline (J Clin Endocrinology & Metabolism, May 2016) without specific medication
• Age > 18 years

Exclusion Criteria for patients with Primary Aldosteronism:

• Chronic kidney disease ≤ 3b (estimated GFR <45 ml/min according to CKD-EPI)
• Active malignancy
• Severe congestive heart failure (NYHA III and IV)
• Liver cirrhosis (Child B and C)
• Acute infection
• Recent major surgical procedures (<3 months)
• Pregnancy
• Contraindications for MRI measurements: cardiac pacemaker, claustrophobia, etc.

Inclusion Criteria for healthy control participants:

- Age > 18 years

Exclusion Criteria for healthy control participants:

• Medical history of chronic disease (such as diabetes, hypertension, chronic kidney disease etc.)
• regular medication
• blood pressure ≥ 140/90 mmHg
• Pregnancy
• Contraindications for MRI measurements: cardiac Pacemaker, claustrophobia, etc.

Patients diagnosed with Primary Aldosteronism Healthy participants