Atrial Natriuretic Peptide (ANP): Function, Testing, and Heart Health

Key Takeaways

• What it is: A 28-amino-acid peptide hormone produced by atrial cardiomyocytes in response to atrial stretch from volume overload or elevated filling pressures.
• Primary function: Promotes natriuresis (sodium excretion), diuresis, and vasodilation; suppresses the RAAS system; lowers blood pressure and reduces cardiac preload.
• Where it comes from: Predominantly the atria of the heart (right and left); also expressed in smaller quantities in ventricles, brain, and other tissues in pathological states.
• Receptor: Natriuretic peptide receptor type A (NPR-A), a membrane-bound guanylyl cyclase that generates cGMP upon ANP binding.
• Clinical testing: Direct ANP measurement is not routine; MR-proANP (midregional pro-ANP) is the stable surrogate used in some European clinical settings. BNP and NT-proBNP are the standard cardiac natriuretic peptide biomarkers in the United States.
• Half-life: Approximately 2 to 5 minutes in plasma; cleared by NPR-C internalization and neutral endopeptidase (neprilysin) degradation.
• Therapeutic relevance: Sacubitril/valsartan (Entresto) inhibits neprilysin, preserving endogenous ANP, BNP, and CNP signaling. This mechanism is one component of the drug's FDA-approved use for HFrEF; prescribing is determined by a licensed provider.

What Atrial Natriuretic Peptide Is and Where It Comes From

Atrial natriuretic peptide (ANP), also called atrial natriuretic factor (ANF), is a 28-amino-acid peptide hormone produced predominantly by cardiomyocytes of the cardiac atria in response to atrial wall stretch. The primary physiological trigger is increased atrial volume or elevated filling pressure — conditions that arise from fluid overload, elevated blood pressure, atrial fibrillation, or cardiac failure. ANP acts on NPR-A receptors in the kidney, vasculature, and adrenal glands to promote sodium and water excretion, dilate blood vessels, and suppress aldosterone and renin secretion — acute physiologic effects that reduce circulating blood volume and vascular resistance in healthy states.

The discovery of ANP in 1981 by de Bold and colleagues was one of the foundational events in modern cardiovascular biology. De Bold, in a 1987 retrospective account published in the Canadian Journal of Physiology and Pharmacology, described the original diuresis in rats observation — a finding that contributed to recognition of the heart as an endocrine organ and preceded the subsequent field of natriuretic peptide research. The peptide was isolated, sequenced, and named within a few years of its discovery. Ichiki and Burnett, in a 2017 review in Circulation Journal, provided a modern ANP synthesis, capturing both the historical depth and continued therapeutic relevance of this molecule.

Ramos and colleagues, in a 2015 interdisciplinary review in Endocrine Connections, characterized cardiac natriuretic peptides and their endocrine role, including why ANP is now considered a full-fledged hormone produced by the atria — a designation that was not obvious when the heart was first conceived primarily as a pump. Chen and Burnett, in an early clinical review in Current Cardiology Reports in 2000, described the role of natriuretic peptides in heart failure, providing the historical clinical context for how ANP research translated to understanding cardiac disease.

ANP Reference Ranges

Direct measurement of mature ANP in clinical practice is uncommon due to the rapid degradation of the peptide in plasma. Where measured, reference values reflect assay-specific methodologies and have limited standardization across laboratories. MR-proANP (midregional pro-ANP), a more stable fragment from the same precursor, is the clinically used surrogate in settings where ANP-pathway assessment is pursued.

• Fasting plasma ANP (healthy adults) — Approximate range: 10 to 77 pg/mL (literature-derived; varies substantially by assay and collection conditions)
• MR-proANP — Heart failure rule-out threshold (non-acute): Below 120 pmol/L per some European guideline applications; varies by assay platform
• MR-proANP — Elevated in heart failure presentations: Values above the laboratory reference interval in symptomatic patients suggest increased atrial wall stress
• ANP in heart failure: Substantially elevated compared to healthy reference values; specific values depend on severity and assay methodology

Reference ranges for ANP vary substantially by laboratory and assay methodology. Direct ANP measurement is not standardized across clinical laboratories. MR-proANP reference intervals vary by assay platform. Your provider will interpret any natriuretic peptide result in the context of your full clinical picture.

How ANP Works in the Body

ANP's physiological effects are mediated primarily through activation of natriuretic peptide receptor type A (NPR-A), a membrane-bound receptor-guanylyl cyclase. When ANP binds NPR-A, the receptor generates cyclic guanosine monophosphate (cGMP) as the intracellular second messenger. Potter and colleagues, in a 2009 handbook chapter, reviewed natriuretic peptide receptor types in comprehensive detail. Potter and colleagues, in a 2006 review in Endocrine Reviews, covered cGMP-dependent signaling downstream of NPR-A, establishing the mechanistic backbone for understanding ANP's diverse effects.

Renal effects: natriuresis and diuresis

In the kidney, NPR-A activation by ANP increases glomerular filtration rate by dilating afferent arterioles and constricting efferent arterioles, simultaneously inhibiting sodium reabsorption in the collecting duct. The result is increased sodium excretion (natriuresis) and water output (diuresis) — the defining properties that gave natriuretic peptides their name. Li and colleagues, in a 2024 study in the American Journal of Physiology Renal Physiology, showed how AT1a receptor deletion alters the hypotensive and natriuretic response to ANP, providing mechanistic depth on the renal angiotensin-ANP interaction relevant to blood pressure physiology.

Vascular effects: vasodilation and blood pressure reduction

ANP directly relaxes vascular smooth muscle through cGMP-mediated dephosphorylation of myosin light chains, producing systemic vasodilation and reduced systemic vascular resistance. This contributes to the blood pressure-lowering effect alongside the volume-reducing renal action. Rubattu and colleagues, in a 2013 review in the Journal of Hypertension, reviewed ANP in vascular function, including its interaction with endothelin and the RAAS system. Vandenwijngaert and colleagues, in a 2019 genetic study in Circulation: Genomic and Precision Medicine, documented genetic variants in NPR-A, providing genetic evidence that links ANP receptor function to population-level blood pressure variation.

RAAS suppression

ANP inhibits renin secretion from the kidney, aldosterone secretion from the adrenal cortex, and the vasoconstrictor actions of angiotensin II. This RAAS antagonism is central to ANP's role as a counterregulatory system opposing the fluid-retaining and vasoconstrictive effects that dominate in heart failure states. Volpe and colleagues, in their 2016 review in Clinical Science, reviewed the natriuretic peptide system and RAAS in heart failure. Volpe and colleagues, in a 2014 review in the International Journal of Cardiology, addressed the cardio-renal dimension, covering how ANP and BNP together regulate the kidney-heart axis in cardiovascular disease.

ANP and lipid metabolism: a non-cardiac action

Beyond its cardiovascular effects, ANP stimulates lipolysis — the breakdown of stored triglycerides — in human adipocytes through a cGMP-dependent mechanism. This is a primate-specific metabolic action not seen in rodents, which explains why it was initially overlooked in animal-model research. Sengenès and colleagues, in a foundational 2002 paper in the American Journal of Physiology, demonstrated natriuretic peptide-dependent lipolysis, establishing ANP as a hormonal driver of fat mobilization during physiological stress. A companion review by Sengenès and colleagues in 2005 in Médecine/Sciences explored a novel lipolytic pathway. This metabolic role is mechanistically interesting but has not been established as a clinically significant driver of systemic body composition.

How ANP Is Synthesized and Cleared

Biosynthesis and processing

ANP is synthesized as a 151-amino-acid precursor (pre-proANP) that is stored in secretory granules in atrial cardiomyocytes. Upon atrial stretch, the precursor is processed to 126-amino-acid proANP, which is then cleaved on the cell surface by the enzyme corin to produce the biologically active 28-amino-acid ANP and the 98-amino-acid N-terminal pro-ANP fragment. Wu and colleagues, in a 2009 review in Kidney International, identified corin as a serine protease responsible for pro-ANP and pro-BNP processing in cardiomyocytes. The midregional fragment of pro-ANP (MR-proANP, amino acids 53 to 90) is more stable than mature ANP and serves as the clinically measurable surrogate for ANP system activation.

Clearance pathways

Active ANP is cleared through two principal mechanisms. NPR-C (natriuretic peptide clearance receptor) binds ANP without signaling and internalizes it for lysosomal degradation — a high-capacity, receptor-mediated clearance system that regulates circulating ANP concentrations. Okolicany and colleagues, in a 1992 study in the American Journal of Physiology, characterized ANP clearance through NPR-C. Neutral endopeptidase (neprilysin) also cleaves and inactivates ANP, the same enzyme targeted by sacubitril. Ralat and colleagues, in a 2011 study in the Journal of Biological Chemistry, characterized IDE in peptide clearance, identifying an under-recognized clearance pathway alongside neprilysin. ANP's very short plasma half-life of approximately 2 to 5 minutes reflects the combined efficiency of these clearance mechanisms.

ANP vs. BNP: Key Differences

ANP and BNP are the two principal cardiac natriuretic peptides in clinical relevance, but they differ in several ways that explain their different clinical applications.

• Source tissue — ANP: Predominantly atrial cardiomyocytes; some ventricular expression in advanced heart failure
• Source tissue — BNP: Predominantly ventricular cardiomyocytes, even under physiological conditions
• Primary secretion trigger — ANP: Atrial stretch from volume overload or elevated atrial filling pressure; rises rapidly with volume changes
• Primary secretion trigger — BNP: Ventricular wall stress from elevated end-diastolic pressure, pressure overload, or myocardial dysfunction
• Half-life — ANP: Approximately 2 to 5 minutes
• Half-life — BNP: Approximately 20 minutes (active BNP); 1 to 2 hours (NT-proBNP fragment)
• Clinical assay availability — ANP: Not routinely assayed; MR-proANP used in some European settings
• Clinical assay availability — BNP/NT-proBNP: Widely available; standard-of-care cardiac biomarker in the United States and internationally
• Diagnostic specificity for heart failure: BNP and NT-proBNP are more specifically linked to heart failure severity because ventricular production correlates more directly with ventricular dysfunction

Castiglione and colleagues, in a 2022 biomarker review in Heart Failure Reviews, covered BNP, NT-proBNP, and MR-proANP in heart failure diagnostics, providing the contemporary framework for understanding how ANP-pathway biomarkers fit into a broader cardiac assessment strategy.

ANP in Heart Failure

In heart failure, atrial dilation from elevated filling pressures drives sustained ANP secretion. Despite chronically elevated ANP levels, the compensatory effects become insufficient as disease progresses — partly because downregulation of NPR-A receptors reduces tissue responsiveness to elevated ANP concentrations, and partly because the downstream cGMP signaling cascade becomes impaired in the setting of chronic pressure overload. Kuwahara, in the 2021 Pharmacology and Therapeutics review, provided a mechanistic review of natriuretic peptides, including impaired ANP signaling that has been described in advanced disease. Volpe and colleagues, in their 2019 review, covered future perspectives for natriuretic peptides, including ANP-based and ANP-enhancing therapeutic directions.

Neprilysin inhibition and ANP amplification

One major modern clinical application of ANP biology is the neprilysin inhibitor sacubitril, the active component of sacubitril/valsartan (Entresto). By blocking neprilysin-mediated degradation of ANP, BNP, and CNP, sacubitril amplifies the effects of the body's own endogenous natriuretic peptide system. Michel and colleagues, in a 2022 Circulation Research paper, showed how proANP metabolism informs sacubitril/valsartan mode of action — supporting the view that ANP preservation may contribute to the drug's effects alongside BNP. McMurray and colleagues, in the PARADIGM-HF trial, reported clinical outcomes in HFrEF patients treated with sacubitril/valsartan versus enalapril — findings that informed subsequent guideline adoption for eligible patients under a clinician's care.

Therapeutic development: carperitide and the IV ANP story

Carperitide (synthetic human ANP) is approved and used for acute decompensated heart failure in Japan, where it is administered by intravenous infusion to rapidly produce natriuresis and vasodilation. This represents the clearest clinical proof-of-concept for exogenous ANP therapy. However, no ANP-based IV therapy has achieved widespread approval or adoption in the United States or Europe. Ezekowitz and colleagues, in the ASCEND-HF methodology paper published in 2009, described the nesiritide trial design that shaped skepticism around exogenous natriuretic peptide therapy in acute heart failure — contributing to the clinical context in which IV ANP analogs failed to become standard of care outside Japan. Sangaralingham and colleagues, in a 2021 Proceedings of the National Academy of Sciences paper, reported NPR-A allosteric modulators that enhance ANP signaling pharmacologically, representing a new direction for ANP-pathway therapeutics that bypasses the delivery challenges of injectable peptides.

ANP Testing: What Is and Is Not Available

Why direct ANP measurement is rarely ordered

Mature ANP degrades rapidly at room temperature, with a half-life of 2 to 5 minutes in plasma. This instability requires specialized collection conditions — immediate chilling of samples on ice, rapid processing, and carefully controlled pre-analytical procedures — that are technically challenging in routine laboratory settings and difficult to standardize across platforms. The result is poor assay reproducibility with direct ANP measurement, which has limited its clinical adoption compared to the more stable NT-proBNP.

MR-proANP as a stable surrogate

MR-proANP (midregional pro-atrial natriuretic peptide, amino acids 53 to 90 of the pro-ANP precursor) is substantially more stable in plasma than mature ANP, making it more amenable to standardized clinical assay. Mueller and colleagues, in the 2019 HFA-ESC guidance, mentioned MR-proANP as an alternative in settings where BNP or NT-proBNP are not available. Castiglione and colleagues, in the 2022 Heart Failure Reviews biomarker review, included MR-proANP with BNP and NT-proBNP as a clinically validated cardiac biomarker for heart failure. MR-proANP is more widely used in European clinical practice than in the United States, where BNP and NT-proBNP assays are fully standardized and universally available.

Fasting requirements and collection logistics

Fasting is not required for natriuretic peptide testing. If ANP or MR-proANP measurement is pursued, sample handling instructions specific to the assay platform should be followed, as pre-analytical stability conditions are critical. For standard BNP or NT-proBNP testing — the clinically relevant practical alternative — fasting is not required and standard venipuncture collection applies.

Which Biomarkers Are Worth Testing Alongside ANP Pathway Assessment

In clinical practice, ANP pathway assessment is most usefully approached through the available surrogate markers. The complementary biomarker picture for cardiac natriuretic peptide evaluation mirrors the context for BNP testing.

• BNP: The standard clinical proxy for natriuretic peptide system activation. More practically available and better standardized than direct ANP measurement. Provides the quantitative cardiac stress marker that ANP biology predicts.
• Troponin (I or T): Distinguishes pressure overload stress (which elevates natriuretic peptides without necessarily elevating troponin) from active myocardial injury. Troponin testing alongside BNP or NT-proBNP completes the acute cardiac biomarker picture.
• hs-CRP: Systemic inflammation drives cardiac remodeling and contributes to heart failure pathophysiology. Tracking inflammation alongside natriuretic peptide markers provides a more complete picture of cardiovascular risk.
• Creatinine and eGFR: Renal function directly affects NT-proBNP clearance and the hemodynamic response to ANP; creatinine alongside natriuretic peptide testing allows accurate interpretation of the full renal-cardiac picture. Cardiovascular health biomarkers sit within a broader longevity-oriented panel.

When to Take This Seriously

ANP biology is relevant clinically in two contexts: understanding the physiology behind elevated BNP results, and understanding the mechanism of heart failure therapies that target the natriuretic peptide system. For a patient who has received a BNP or NT-proBNP result, understanding that both BNP and ANP reflect cardiac wall stress through the same receptor system clarifies why the clinical guidelines use these markers as the primary diagnostic and prognostic tools for heart failure evaluation.

Direct ANP testing is rarely clinically actionable in the United States — BNP and NT-proBNP are the practical tools. Elevated BNP results are interpreted in clinical context; the BNP test page covers reference ranges and physiology in detail. A comprehensive biomarker panel integrates cardiac, inflammatory, and metabolic markers in a single draw.

IMPORTANT SAFETY INFORMATION

Atrial natriuretic peptide (ANP) is an endogenous hormone. Direct measurement of ANP is not a standard clinical test in most settings. This article is provided for educational and informational purposes only and does not constitute medical advice, diagnosis, or treatment guidance.

Clinical evaluation of natriuretic peptide pathway activity is typically performed through BNP or NT-proBNP testing in the context of cardiac symptoms. These tests must be ordered and interpreted by a qualified healthcare provider. The MR-proANP biomarker referenced in this article is used in some European clinical settings; its availability and clinical application should be directed to your provider.

Sacubitril/valsartan (Entresto) is an FDA-approved prescription medication for heart failure with reduced ejection fraction. Its mechanism involves natriuretic peptide amplification. This discussion is for educational context only and does not constitute prescribing guidance. Consult a qualified healthcare provider regarding medication eligibility.

Disclaimer: This article is for informational purposes only and does not constitute medical advice. ANP is an endogenous cardiac hormone; direct ANP testing is not routine in most clinical settings. Clinical natriuretic peptide assessment is typically performed through BNP or NT-proBNP testing by a qualified healthcare provider.