BNP

Where it comes from

Made in

Ventricular heart muscle (first found in pig brain, hence the name)

Sent out by

Stretch of the ventricle wall; made on demand rather than stored

Acts on

• Kidney
• Blood vessels
• Adrenal cortex (aldosterone)
• Heart muscle

What it does

• Sheds sodium and water and relaxes vessels
• Opposes the renin-angiotensin-aldosterone system
• Slows the scarring and thickening of the heart muscle

In medicine

• BNP and NT-proBNP are the blood tests that rule heart failure in or out and track it
• Nesiritide, recombinant BNP, was approved for acute heart failure in 2001 ¹; a 7,141-patient trial found no gain in survival or breathlessness, and it is no longer marketed in the United States ²
• Sacubitril, in sacubitril/valsartan, blocks neprilysin so that BNP lasts longer; on it, BNP rises and NT-proBNP is the test to follow ³

Beyond the body’s own use

• The thresholds are not fixed. BNP falls as body mass index rises, and in 2,707 people it tracked lean mass more closely than fat mass, which argues against the usual clearance-receptor explanation for the obesity effect ⁴
• Age raises it and kidney failure raises it, so one cut-off over-diagnoses heart failure in the old and the uraemic and under-diagnoses it in the obese ⁴
• A neprilysin inhibitor raises BNP, because neprilysin is what destroys it: in PARADIGM-HF the median went from 202 to 235 ng/L in the first two months and doubled in about one patient in five, while NT-proBNP did not behave that way; BNP still predicted outcome as well as before ³
• There is no use for BNP outside medicine. It is a test, and the one attempt to give the peptide back as a treatment did not help the patients who received it ²