Does the Heart Produce Hormones? Its Endocrine Function Explained

The heart produces at least two major hormones that circulate through the bloodstream and regulate organs throughout the body. Atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP) are polypeptide hormones manufactured by heart muscle cells, and their discovery in the early 1980s fundamentally changed how scientists view the heart. Far from being just a mechanical pump, the heart functions as a genuine endocrine organ whose hormonal output influences blood pressure, kidney function, fat metabolism, and more.

How the Heart Was Recognized as an Endocrine Organ

For most of modern medicine’s history, the heart was understood purely as a muscular pump. That changed in 1981, when researchers reported that extracts taken from the heart’s upper chambers (the atria) contained a substance capable of triggering massive water and salt excretion by the kidneys, raising blood cell concentration, and lowering blood pressure.1PubMed. On the shoulders of giants: the discovery of atrial natriuretic factor The substance was soon named atrial natriuretic factor, or ANF (also called ANP for atrial natriuretic peptide).

The clues had actually been hiding in plain sight for decades. Electron microscopy had revealed that atrial muscle cells contained storage granules that looked strikingly similar to those found in known hormone-producing cells. Nobody had connected those granules to hormonal activity until systematic studies showed that the granules were filled with a polypeptide hormone that is diuretic, lowers blood pressure, and suppresses the secretion of renin and aldosterone, two powerful hormones that raise blood pressure and retain salt.2PubMed. Atrial natriuretic factor: a hormone produced by the heart This was the moment the heart officially joined the ranks of endocrine organs.

Shortly after ANP’s discovery, a related hormone called brain natriuretic peptide (BNP) was identified. Despite its name, BNP is produced primarily by the heart’s ventricles, not the brain. Together, ANP and BNP form the core of a hormonal system that now underpins both heart failure diagnostics and several drug therapies.3PubMed. Thirty years of research on atrial natriuretic factor: historical background and emerging concepts

What Triggers the Heart to Release Its Hormones

The main stimulus is mechanical stretch. When blood volume increases or the heart is under pressure overload, the walls of the atria physically stretch, and this stretching is the signal that tells atrial muscle cells to release ANP into the bloodstream. In animal experiments, an acute expansion of blood volume roughly quadrupled circulating ANP levels within minutes.4PubMed. Pressor hormones regulate atrial-stretch-induced release of atrial natriuretic peptide in the pithed rat Microscopy studies have shown that part of this release mechanism involves the hormone-containing granules physically migrating toward the cell surface in response to stretch, preparing for rapid secretion.5PubMed. Stretch-induced centrifugal movement of atrial specific granules–a preparatory step in atrial natriuretic peptide secretion

BNP responds to stretch too, but through a slightly different mechanism. When researchers increased right atrial pressure in isolated hearts, BNP gene activity rose over one to two hours, driven by new gene transcription rather than just the dumping of pre-made hormone from granules.6PubMed. Involvement of transcriptional and posttranscriptional mechanisms in cardiac overload-induced increase of B-type natriuretic peptide gene expression This means ANP can be released almost instantly in response to a sudden volume spike, while BNP production ramps up more gradually as the heart sustains higher workloads over time. That timing difference turns out to be clinically useful, because persistently elevated BNP tends to signal chronic heart problems rather than a momentary blip in fluid balance.

What These Hormones Do Once They Enter the Blood

Both ANP and BNP travel through the circulation and bind to receptors on target cells. The principal receptor is called natriuretic peptide receptor-A (NPRA), which produces a signaling molecule called cGMP inside the target cell.7PubMed Central. Molecular Signaling Mechanisms and Function of Natriuretic Peptide Receptor-A in the Pathophysiology of Cardiovascular Homeostasis That single second messenger triggers a cascade of downstream effects across multiple organ systems.8PubMed. Natriuretic Peptides as Multisystem Regulators: From Clinical Biomarkers to Therapeutic Targets in Cardio-immunology

The kidneys are the most obvious target. ANP and BNP increase the rate at which blood is filtered in the kidneys, promote the excretion of sodium and water, and directly oppose the renin-angiotensin-aldosterone system, a powerful hormonal axis that otherwise works to retain salt and raise blood pressure.9PubMed Central. Protective Renal Effects of Atrial Natriuretic Peptide: Where Are We Now? ANP achieves this by acting at multiple points along the kidney’s tubular system, shutting down sodium pumps and channels that would otherwise pull sodium (and water along with it) back into the blood.10PubMed Central. ANP-induced signaling cascade and its implications in renal pathophysiology

Beyond the kidneys, natriuretic peptides reduce sympathetic nervous system activity (the body’s “fight or flight” signaling), lower cardiac output, curb the growth of heart muscle cells and the scarring cells called fibroblasts, and reduce overall blood pressure.11PubMed. The renal and cardiovascular effects of natriuretic peptides The net effect is a carefully calibrated counter-pressure system: when blood volume or pressure climbs too high, the heart releases hormones that bring it back down.

Fat Burning and Metabolic Effects

One of the more surprising discoveries about cardiac hormones is that they promote fat breakdown. ANP and BNP stimulate lipolysis in human fat cells through a cGMP-dependent pathway that is entirely separate from the more familiar adrenaline-driven fat-burning route.12PubMed. Control of lipolysis by natriuretic peptides and cyclic GMP When ANP levels rise, whether from drugs or from exercise, fat mobilization increases measurably.

More recent work has linked natriuretic peptides to heat generation in fat tissue and to the oxidative capacity of skeletal muscles, suggesting that the heart’s hormonal output plays a broader role in energy expenditure than anyone suspected when ANP was first discovered.13PubMed Central. The Effects of Exercise on Natriuretic Peptides in Individuals without Heart Failure The research is still evolving, but the direction is clear: the heart’s hormones do more than manage fluid balance. They participate in whole-body metabolism.

BNP and NT-proBNP as Heart Failure Biomarkers

When heart muscle cells produce BNP, they actually manufacture a larger precursor molecule that gets clipped into two fragments: the active BNP hormone and an inactive leftover piece called NT-proBNP. Both fragments end up in the bloodstream, and both can be measured with a blood test. In heart failure, the ventricles are under chronic stress, and BNP production soars. This makes BNP and NT-proBNP powerful diagnostic tools. Clinicians use them to help diagnose heart failure, track how well treatment is working, and predict outcomes.14PubMed. Comparison of BNP and NT-proBNP in Patients With Heart Failure and Reduced Ejection Fraction

In patients with heart failure, NT-proBNP levels are dramatically higher than in patients without the condition, and the elevation persists across different heart failure subtypes, whether the heart’s pumping ability is severely reduced or relatively preserved.15European Journal of Heart Failure. Heart failure phenotypes determine NT-proBNP levels in haemodialysis patients independent of volaemia NT-proBNP correlates closely with how stretched the heart is and how high filling pressures have climbed, which is exactly what makes it such a reliable window into cardiac stress. Ordering an NT-proBNP test is now routine in emergency departments when a patient arrives short of breath and heart failure is on the list of possible causes.

Heart Failure Drugs That Harness Cardiac Hormones

If the heart’s own hormones lower blood pressure and reduce fluid overload, a logical drug strategy is to stop the body from breaking them down so fast. That is exactly the principle behind sacubitril/valsartan, a medication that combines a blocker of the blood-pressure-raising renin-angiotensin system with an inhibitor of neprilysin, the enzyme that degrades natriuretic peptides. By slowing the clearance of ANP and BNP, the drug lets the heart’s beneficial hormones linger longer in the bloodstream.

In a landmark trial, sacubitril/valsartan was shown to reduce the risk of cardiovascular death or heart failure hospitalization compared to enalapril, a standard blood-pressure medication, in patients with chronic heart failure and reduced pumping ability.16PubMed Central. Sacubitril/Valsartan: Neprilysin Inhibition 5 Years After PARADIGM-HF In patients hospitalized for acute worsening of heart failure, starting sacubitril/valsartan led to a roughly 47% reduction in NT-proBNP levels from baseline over the first two months, compared to about a 25% reduction with enalapril alone.17PubMed. Angiotensin-Neprilysin Inhibition in Acute Decompensated Heart Failure The drug has become a cornerstone of modern heart failure therapy, and its success rests squarely on the recognition that the heart is an endocrine organ whose hormones can be pharmacologically amplified.

How the Body Clears Natriuretic Peptides

Like all hormones, ANP and BNP need to be broken down after they have done their job; otherwise, their effects would run unchecked. Two main clearance pathways exist. The first is enzymatic degradation by neprilysin (also called neutral endopeptidase), which chops the peptides into inactive fragments. The second is a dedicated clearance receptor, called natriuretic peptide receptor-C, which pulls ANP out of the circulation and tags it for disposal inside cells.18PubMed Central. Natriuretic peptide metabolism, clearance and degradation

Interestingly, ANP and BNP appear to rely on these pathways to different degrees. In patients with chronic heart failure, blocking neprilysin raised both ANP and BNP levels, confirming that both hormones are degraded by the enzyme. But flooding the clearance receptors with a large infusion of ANP did not change BNP levels at all, suggesting that BNP does not depend on the clearance receptor pathway for its removal.19PubMed. Clearance of brain natriuretic peptide in patients with chronic heart failure: indirect evidence for a neutral endopeptidase mechanism but against an atrial natriuretic peptide clearance receptor mechanism The inactive fragment NT-proBNP has an even longer half-life in the blood than active BNP because it is not degraded by neprilysin at all; it is cleared mainly by the kidneys. That longer half-life is one reason NT-proBNP makes a convenient blood test, as levels are more stable and easier to measure.

Other Signaling Molecules the Heart Produces

ANP and BNP get the most attention, but the heart produces or hosts a surprisingly long list of additional signaling molecules that act locally, on neighboring tissues, or even at a distance.

The takeaway from this growing list is that the heart is not simply pumping and occasionally releasing ANP. It is a complex signaling hub, producing hormones and local factors that regulate its own growth, the tone of blood vessels, and the behavior of distant organs.

Exercise and the Surge in Cardiac Hormones

If you have ever wondered whether your heart releases hormones while you work out, the answer is a clear yes. In healthy people without heart disease, resting natriuretic peptide levels are not elevated, but strenuous endurance exercise drives significant increases.13PubMed Central. The Effects of Exercise on Natriuretic Peptides in Individuals without Heart Failure During bicycle exercise, plasma ANP rose by roughly 236%, while BNP increased by about 41%.25PubMed. Effects of exercise on natriuretic peptides and cardiac function in man The two hormones correlated with different aspects of cardiac performance: ANP tracked more closely with heart rate and the size and filling of the left atrium, while BNP related more to left ventricular size and function.

The exercise-induced spike in natriuretic peptides appears to come from transient stress on the heart walls as the heart pumps harder and faster, combined with metabolic changes inside the heart muscle cells themselves. This is not a sign of damage. It may actually be protective, with the released hormones exerting growth-regulating and cytoprotective effects on the heart. The connection to fat metabolism is also relevant here: the rise in ANP during exercise may contribute to lipid mobilization, adding a hormonal dimension to the familiar story of burning fat during a workout.12PubMed. Control of lipolysis by natriuretic peptides and cyclic GMP

How Natriuretic Peptide Receptors Evolved

The natriuretic peptide system is ancient, but it did not emerge all at once. Researchers tracing the evolutionary history of this hormone-receptor pair found something counterintuitive: the receptors appear to have evolved before the hormones that bind to them. Peptides with some structural resemblance to natriuretic peptides have been found in invertebrates, but a detailed analysis of the receptor’s binding pocket shows that it was completely remodeled in mammals.26PubMed Central. Natriuretic peptides appeared after their receptors in vertebrates Multiple lines of evidence, including molecular modeling of how the peptides fit into their receptors, suggest that the hormones as we know them evolved after the receptor machinery was already in place.

This is not as strange as it sounds. In evolutionary biology, a pre-existing receptor can get “hijacked” by a new signaling molecule that happens to fit its binding pocket, and selection then refines both partners over time. For the heart, this means that the endocrine function we see today was built on receptor scaffolding that originally served other purposes. The mammalian natriuretic peptide system, with its precise responses to cardiac stretch and its far-reaching effects on kidneys, blood vessels, and fat tissue, is a relatively recent evolutionary innovation layered onto much older molecular infrastructure.

Receptor Variants That Cannot Signal

One wrinkle in the natriuretic peptide story involves alternative versions, or isoforms, of the NPRA receptor. Researchers have identified at least three naturally occurring splice variants of the receptor that are expressed in human tissues. When cells were engineered to produce these variant receptors and then exposed to ANP, none of the three variants produced any cGMP, the signaling molecule that drives all of the downstream effects of natriuretic peptides. Only the standard full-length receptor responded normally, showing a dose-dependent increase in cGMP production.27PubMed Central. Unveiling the potential role of natriuretic peptide receptor a isoforms in fine-tuning the cGMP production and tissue-specific function

The existence of non-signaling receptor variants raises an interesting possibility: different tissues may use the ratio of active to inactive receptors to fine-tune how strongly they respond to ANP and BNP. A tissue that expresses mostly inactive isoforms would be relatively insensitive to the heart’s hormones, while a tissue expressing the full-length receptor would respond robustly. This kind of tissue-specific tuning could explain why natriuretic peptides have such selective effects on certain organs. The research is still early, but it hints at a more sophisticated regulatory layer than the simple picture of “heart releases hormone, target organ responds.”