Treating tiny benign tumours in the adrenal glands may prevent huge numbers of cases of high blood pressure, say researchers.
The team at the University of Cambridge and Addenbrooke’s Hospital think that up to 10% of cases may be caused by the growths.
Their study, published in Nature Genetics, said young patients could be freed from a lifetime of medication.
The British Heart Foundation said it was an “exciting development”.
High blood pressure can have fatal consequences as it increases the risk of heart attacks and stroke.
Most cases are caused by lifestyle choices such as smoking and diet.
Researchers had already found that large growths in the adrenal glands, which sit on the kidneys and produce hormones, could raise blood pressure. An operation to remove any tumours can reduce blood pressure.
Now the researchers in Cambridge have found that much smaller growths, in a different part of the glands, are producing the same effect.
Both increase the amount of aldosterone made in an adrenal gland. Release of this hormone regulates the kidneys to retain more salt in the body, so increasing blood pressure.
Around 5% of high blood pressure cases are down to the large growths, but the researchers argue that the discovery of the small tumours means far more people have preventable blood pressure.
Prof Morris Brown told the BBC: “We think it could be twice that amount. My guess is around 10%, so it could be as many as one million people [in the UK].”
Living with high blood pressure for too long causes changes in the heart and arteries that mean that operations later in life may not reverse the condition.
“We can’t go looking for the 50 and 60-years-olds, we’ve missed the boat. We should go looking for the 30-year-olds,” said Prof Brown.
Prof Jeremy Pearson, of the British Heart Foundation, said: “It is an exciting development, as this group of patients can be completely cured of high blood pressure once they have been identified, so the quicker they are diagnosed the better.”