This study is a observational study applying 24-hour microdialysis methodology to perform dynamic multisteroid adrenal hormone profiling of patients with suspected or confirmed PA. Simultaneous registration of blood pressure, tissue glucose, sleep pattern, activity level and food intake registration may be performed. The overall objective is to develop a novel, sensitive, fast and user-friendly diagnostic procedure for PA, using multimodal data capture including dynamic multisteroid hormone profiling from microdialysis fluid.

Primary aldosteronism is the most common cause of secondary hypertension. Primary aldosteronism has increased risk of organ complications compared with primary hypertension if left undiagnosed and without specific treatment. However, the current diagnostic work-up is a cumbersome, multistep process, relying on repeated single time point measurements of aldosterone, not capturing the rhythmic nature of aldosterone and related adrenal hormone secretion.

In this study we will apply the U-Rhythm microdialysis sampling system for 24-hour measurements from subcutaneous microdialysis fluid, analysed with LC/MS-MS methodology for dynamic multisteroid adrenal hormone profiling. We will further compare multisteroid hormone profiling results with variations in blood pressure and tissue glucose, sleep pattern, activity level and food intake.

The overall objective of the study is to develop a novel, sensitive, fast and user-friendly diagnostic procedure for PA, using multimodal data capture including 24-hour dynamic multisteroid hormone profiling from microdialysis tissue.

Primary objective

• Assess dynamic multisteroid rhythmicity in microdialysis fluid of aldosterone, precursors and metabolites of the mineralocorticoid and glucocorticoid pathway, compared to standard diagnostic work-up in patients with suspected or confirmed PA.

Secondary objectives

• Quantify the influence of salt and volume loading during diagnostic saline infusion test on multisteroid adrenal rhythmicity.
• Quantify the influence of glucocorticoids/ACTH suppression on multisteroid rhythmicity.
• Quantify the influence of cortisol co-secretion on multisteroid rhythmicity in PA.
• Quantify influence of blood pressure, pulse, sleep, food intake and movement on multisteroid rhythmicity in PA.

Inclusion criteria Age 18 to 70 years Suspected PA admitted for diagnostic saline infusion testing or confirmed PA diagnosis according to Endocrine Society criteria.. Written informed consent

Exclusion criteria

• Age <18 or > 70 years.
• Pregnancy.
• Known adrenal failure and/or on steroid therapy (oral, inhaled, parenteral or topical) or other interfering medication.

Adult patients with suspected primary aldosteronism admitted to Haukeland University for diagnostic saline infusion test will be invited for study inclusion for dynamic microdialysis during saline infusion testing. If the diagnosis is confirmed, a repeated microdialysis sampling will be performed without saline infusion suppression.

Additional patients with confirmed primary aldosteronism admitted to Haukeland University Hospital for subtyping with adrenal vein sampling will be invited for study inclusion for microdialysis without and during dexamethasone suppression.