A clinical trial has shown a new type of medical scan can identify specific adrenal gland nodules responsible for excess hormone secretion linked to high blood pressure. The new scan offers the first simple diagnostic tool for what is thought to be the cause of hypertension in up to 10% of people.
Hypertension is often brought on by a variety of environmental, genetic and lifestyle factors, but for some people it can be caused by a single hormonal issue. Known as primary aldosteronism, high blood pressure can be caused by excessive adrenal gland production of a hormone called aldosterone.
It's estimated between five and 10% of hypertension cases are caused by this hormone dysfunction, and it can be fixed through a simple surgical procedure to remove the problematic adrenal gland nodules. But primary aldosteronism is rarely diagnosed in patients due to the lack of a simple diagnostic test.
This newly developed test uses a molecule called metomidate, which tends to accumulate specifically in adrenal gland nodules that produce excessive levels of aldosterone. The metomidate used in the test is tagged with a radioactive tracer, so when a patient is imaged through computed tomography (CT) only their nodules excessively producing aldosterone will light up.
“These aldosterone-producing nodules are very small and easily overlooked on a regular CT scan," said study co-author Morris Brown. "When they glow for a few minutes after our injection, they are revealed as the obvious cause of hypertension, which can often then be cured."
In a newly published study, researchers have reported on the results of a clinical trial testing the accuracy of this diagnostic CT scan. Over 100 patients with clinically confirmed primary aldosteronism were recruited and the simple scan was found to be as effective at diagnosing the condition as a more complicated, and rarely performed, procedure known as adrenal vein sampling.
The findings present this new CT scan as a novel method for detecting cases of hypertension that can be surgically cured. However, the technology faces a significant hurdle that needs to be overcome before it can be widely deployed.
The carbon-11 radiotracers used in the research have a notoriously short half-life of around 20 minutes. This means the radioactive molecules used in the CT scans must be created on-site and immediately used. Most major health facilities don't have on-site cyclotrons to synthesize radiotracers.
A new trial is now underway testing a different form of metomidate, modified to have a two-hour radioactive half-life. If this new tracer is just as effective it will make the test much more accessible to most hospitals with PET scanning facilities.
Brown is confident this novel test will be widely available soon and for the first time give doctors and patients a simple way to diagnose a type of hypertension that can be surgically cured.
"Until now, 99% are never diagnosed because of the difficulty and unavailability of tests," said Brown. "Hopefully this is about to change.”
The new study was published in Nature Medicine.
Source: Queen Mary University of London
