Natriuretic peptides are cardiac-derived peptide hormones that regulate vascular tone, sodium balance, and circulating volume. B-type natriuretic peptide (BNP) was first isolated from porcine brain tissue in 1988 and was therefore originally termed “brain natriuretic peptide.” It was later recognized that the dominant source of BNP in humans is the heart, with release increasing particularly in response to ventricular wall stress and distension.

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BNP is produced by cardiomyocytes in both the atrial and ventricular myocardium. BNP gene expression occurs in both chamber types, but in the normal heart the atria are the main site of expression. In diseases that affect the ventricles, ventricular BNP gene expression rises markedly. This chamber-shift in expression has contributed to the common misconception that BNP is primarily a “ventricular hormone”.

 

BNP belongs to the natriuretic peptide family, which includes atrial natriuretic peptide (ANP), C-type natriuretic peptide, D-type natriuretic peptide, and urodilatin. BNP is synthesized as proBNP, which is cleaved into the biologically active BNP hormone and the biologically inactive amino-terminal fragment (NT-proBNP). NT-proBNP is released into the circulation alongside BNP and does not appear to have biological activity.

 

BNP exerts its effects by binding to natriuretic peptide receptors, promoting natriuresis and diuresis, vasodilation, and suppression of the renin–angiotensin–aldosterone system. Natriuretic peptides also inhibit myocardial hypertrophy and adverse remodeling.

 

BNP has an estimated plasma half-life of about 20 minutes, whereas NT-proBNP has a longer half-life of about 120 minutes. This difference largely explains why NT-proBNP concentrations are typically six-fold higher than BNP concentrations, despite equimolar release.

 

BNP production in cardiomyocytes is also upregulated by inflammatory cytokines, which can stimulate BNP synthesis independently of hemodynamic load. Clinically, this is reflected in conditions such as myocarditis, where BNP levels may be higher than expected based on measured hemodynamics alone.

 

BNP and NT-proBNP concentrations are influenced by several comorbidities. Levels tend to be higher in chronic kidney disease, type 2 diabetes, and acute coronary syndromes, while obesity is associated with lower BNP/NT-proBNP concentrations. With aging, declining renal function may contribute to higher NP levels even in the absence of overt heart failure, as NP concentrations rise with decreasing glomerular filtration rate. In addition, some older individuals who appear clinically well may have subtle, early cardiac dysfunction that is not detected by current routine methods.

 

In cardiac disease, BNP and NT-proBNP rise primarily due to myocardial stress and volume/pressure overload. Although widely used in the evaluation of heart failure, BNP/NT-proBNP can be elevated in other cardiac conditions, including right ventricular failure, acute myocardial infarction, congenital heart disease, and valvular heart disease. They may also be increased in non-cardiac states that raise intravascular volume or wall stress, such as sepsis, anemia, Cushing syndrome, hyperaldosteronism, hypertension with left ventricular hypertrophy, and cirrhosis.

 

Natriuretic peptides in the diagnosis of heart failure

Natriuretic peptides (NPs) have a central role in the diagnostic work-up of suspected heart failure.

 

A low NP concentration in a previously untreated, symptomatic patient with a non-acute onset of symptoms rules out heart failure. The used rule-out thresholds are: BNP <35 pg/mL and NT-proBNP <125 pg/mL (ESC/AHA/ACC/HFSA).

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At the guideline level, these relatively low rule-out cut-offs are applied to all age groups, including older adults. Thus, any NP value above the rule-out threshold can justify further cardiology assessment—even though, in an older patient, the same “mild elevation” may still fall within an age-typical range. Current ESC and AHA/ACC/HFSA guidelines do not use age-stratified BNP/NT-proBNP cut-offs, because “normal” NP concentrations show wide inter-individual variability and there are no well-established higher age-specific rule-out thresholds that reliably preserve sensitivity (i.e., are “safe enough” for excluding heart failure) in older people.

 

So neither the ESC nor the AHA/ACC/HFSA heart failure guideline uses age-stratified BNP/NT-proBNP cut-offs in their algorithms. However, many clinicians refer to age-stratified NT-proBNP “rule-in” thresholds from studies/consensus statements. These thresholds were derived from acute dyspnoea studies in emergency department settings:

• <50 years: NT-proBNP >450 pg/mL
   

• 50–75 years: >900 pg/mL
   

• >75 years: >1800 pg/mL
   

Population studies in healthy adults aged ≥65 years show upper reference limits (97.5th percentile) for NT-proBNP of around 600–800 pg/mL, meaning many healthy older individuals exceed the guideline rule-out value of 125 pg/mL.

Several large population cohorts provide reasonably robust age-specific reference ranges:

• <50 years: 97.5th percentile for NT-proBNP ~80–150 pg/mL (lower in men, higher in women)
   

• Healthy adults ≥70–80 years: rises to about ~500–800 pg/mL
   

In a Generation Scotland analysis of an unselected general population aged ≥80 years, the 97.5th centile was very high (men ~6,792 pg/mL; women ~2,704 pg/mL). In this analysis, about one-third of individuals aged ≥80 years had NT-proBNP ≥400 pg/mL.

 

ESC and AHA/ACC/HFSA heart failure guidelines also do not provide rule-in thresholds for chronic heart failure. The earlier guideline statement that NT-proBNP >2000 ng/L or BNP >400 ng/L makes heart failure very likely reflects older concepts and is retained in NICE and several national pathways; these values were originally derived as “rule-in” thresholds from acute dyspnoea studies.

 

Age, sex and renal function effects on natriuretic peptides

NT-proBNP concentrations rise markedly with age (often up to 6–7-fold higher in very old adults compared with young adults), and values are consistently higher in women than in men.

 

NP concentrations correlate (quite weakly) with heart failure severity, including NYHA class, filling pressures and exercise capacity. With effective diuretic therapy and decongestion, symptoms may improve and NP levels fall quickly; this can lower values below usual diagnostic thresholds and reduce sensitivity for diagnosing if a patient is on diuretic therapy.

 

Renal dysfunction increases NP concentrations, particularly NT-proBNP, which is more dependent on renal clearance than BNP:

• Mild renal impairment (eGFR >45 mL/min/1.73 m²) usually has little or no clinically relevant effect on NP cut-offs, and standard diagnostic thresholds can generally be used.

• Moderate renal impairment (eGFR 31–45 mL/min/1.73 m²) is associated with roughly up to a two-fold increase in baseline NT-proBNP compared with patients with normal renal function at the same heart failure severity.

• Severe renal impairment (eGFR 15–30 mL/min/1.73 m²) can lead to two- to several-fold higher NT-proBNP concentrations even without clear clinical deterioration. In this group, guidelines emphasise using serial trends over time combined with the overall clinical picture.

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Natriuretic Peptides in Obesity

Obese patients have lower natriuretic peptide (NP) levels, and diagnostic cut-offs should be reduced to maintain sensitivity. The Heart Failure Association of the ESC recommends using NP cut-off concentrations 50% lower in patients with obesity (BMI ≥30 kg/m²). Recent ACC/HF documents largely follow the same principle, effectively adopting the “50% lower threshold in obesity” concept.

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Rule of thumb for NT-proBNP suppression:

• BMI 25–29.9: ≈20% lower than expected
   

• BMI ≥30: ≈50% lower than expected

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Sacubitril/valsartan and natriuretic peptides

Sacubitril is a neprilysin inhibitor. Neprilysin breaks down BNP, but it does not degrade NT-proBNP.

 

So when sacubitril is initiated BNP breakdown is inhibited which leads to reduced BNP clearance and thus measured BNP may increase and BNP can be misleadingly high even if the patient is doing better.

 

NT-proBNP is not not a neprilysin substrate and its level mainly reflects proBNP production. As HF improves, NT-proBNP tends to decrease.

 

In patients on sacubitril/valsartan, NT-proBNP is preferred for monitoring HF status.

 

PARADIGM-HF

BNP increase:

Median BNP at baseline: 202 ng/L
After 8–10 weeks of sacubitril/valsartan: 235 ng/L (128–422) meaning 16% median increase
Distributionally BNP doubled in 18% of patients and tripled in 6% by 8–10 weeks.
So a modest rise in BNP can be expected, with a minority showing ≥2-fold increases.

 

NT-proBNP decrease:

NT-proBNP fell by ≈30% during sacubitril/valsartan treatment compared with little change on enalapril.

 

PROVE-HF
Median NT-proBNP went from 816 pg/mL to 455 pg/mL at 12 months meaning 44% reduction.

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What change in BNP/NT-proBNP is significant?

There is both analytical variation (assay / laboratory factors) and biological intra-individual variation (pulsatile secretion, hemodynamic changes) and together, these make comparison of natriuretic peptide values challenging, especially between different patients.

 

Reference change value (RCV) attempts to answer the question: how large must a change be to exceed the combined analytical and biological variability? RCVs for natriuretic peptides are very large. Reviews and heart failure management discussions often state that a “>30% change in BNP/NT-proBNP is clinically meaningful” even though classical studies derive that for a confidence of 95% the changes would need to be bigger. ESC–HFA 2019 natriuretic peptide guidance describes an individual “dry” NP value and suggests that approximately a doubling (100% increase) from that baseline strongly indicates a change in clinical status.

 

With stricter RCV math it can be stated that for NT-proBNP (serial measurements) >50% increase strongly suggests true worsening beyond expected variability and >50% decrease typically indicates true improvement.

 

Many reviews and HF management documents consider a >30% change in BNP/NT-proBNP clinically meaningful, although classical RCV studies suggest larger changes are needed for 95% confidence. ESC–HFA 2019 highlights an individual “dry” NP value and notes that an ≈100% increase from this baseline strongly indicates a change in clinical status. Using stricter RCV criteria, a >50% increase in NT-proBNP strongly suggests true worsening, and a >50% decrease typically reflects true improvement.

 

Neither the 2021 ESC HF guideline nor the 2022 AHA/ACC/HFSA HF guideline give a percentage change that counts as significant for serial BNP/NT-proBNP in routine follow-up.

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NYHA class and BNP/NT-proBNP

Natriuretic peptides go up with each higher NYHA class. In an individual there is huge overlap between classes, so you cannot reliably infer NYHA class from a peptide value.

 

Typical NT-proBNP values by NYHA class

A large HFrEF cohort reports NT-proBNP by NYHA class like this:

• NYHA I: mean ≈ 1,000 pg/mL

• NYHA II: mean ≈ 1,600–1,700 pg/mL

• NYHA III: mean ≈ 3,000 pg/mL

• NYHA IV: mean ≈ 3,500+ pg/mL
   

The MEAN VALUES increase steadily, but the 5th–95th percentile ranges overlap heavily between classes. For example, a “high” NYHA I patient may have a higher NT-proBNP than a “low” NYHA III.

 

A PARADIGM-HF analysis looked at NT-proBNP vs NYHA class and quantified how much the distributions overlap.

• NYHA I vs II: ~93% overlap

• NYHA I vs III: ~79% overlap

• NYHA II vs III: ~83% overlap