Adrenomedullin

Adrenomedullin (ADM) is a 52-amino acid peptide first isolated in 1993 by Kazuo Kitamura and colleagues from human pheochromocytoma (adrenal medulla tumor) tissue. Despite its name suggesting adrenal origin, ADM is expressed ubiquitously throughout the body, with particularly high expression in endothelial cells, vascular smooth muscle, the heart, lungs, kidneys, and gastrointestinal tract. It belongs to the calcitonin gene-related peptide (CGRP) superfamily and acts through the calcitonin receptor-like receptor (CLR) complexed with receptor activity-modifying proteins (RAMPs), particularly RAMP2 and RAMP3.

ADM is one of the most potent endogenous vasodilators, producing sustained hypotension when administered intravenously. Its cardiovascular effects include vasodilation, positive inotropy, natriuresis (sodium excretion), and diuresis. Beyond hemodynamic effects, ADM has anti-inflammatory, anti-oxidant, anti-apoptotic, and anti-microbial properties. It stabilizes the endothelial barrier, reducing vascular permeability — a particularly important function in sepsis and inflammatory conditions where vascular leak is a critical pathological mechanism.

In clinical medicine, ADM has gained significant attention as a biomarker. The stable mid-regional fragment of proadrenomedullin (MR-proADM) is measured as a surrogate for ADM levels (since ADM itself is rapidly cleared from plasma). Elevated MR-proADM levels are strong predictors of mortality in sepsis, community-acquired pneumonia, heart failure, and myocardial infarction. MR-proADM has been incorporated into clinical decision-making algorithms, particularly for pneumonia severity assessment.

Therapeutic development of ADM has focused on sepsis, where its endothelial-stabilizing and anti-inflammatory properties are particularly relevant. Adrecizumab, a non-neutralizing anti-ADM antibody that stabilizes circulating ADM and redirects it to the vasculature, has been investigated in clinical trials for septic shock. The approach of modulating ADM bioavailability rather than blocking it represents a novel pharmacological strategy.