The endocrine system is composed of several glands whose main function is to secrete hormones into the blood.

Hormones (amines, peptides and proteins, steroid hormones) serve as a major means of communication between different organs and tissues and regulate a variety of essential physiological processes, frequently including regulatory feedback loops.

Therefore, endocrine diseases - which may lead to increased or decreased hormone production - are complex disorders, and laboratory tests play an important role in diagnosis and treatment.

A relevant example for an endocrine disorder is Primary Aldosteronism (PA), whose main symptoms include hypertension. Originally assumed to account for less than 1% of hypertensive patients, recent data suggest a PA share as high as 5 - 15%. Detecting PA is all the more important since PA patients have a higher cardiovascular morbidity and mortality than patients with essential hypertension, and given that specific PA treatments are available. The Endocrine Society (1) PA Guideline recommends determination of the plasma aldosterone/renin ratio (ARR) to detect PA in patient groups with relatively high PA prevalence, including patients suffering from severe or drug resistant hypertension.