Cortisol in late-night saliva may work as well as 24-hour urine test
Study tested both methods to check Cushing's remission after radiotherapy
Measuring cortisol in a small sample of saliva collected late at night may work just as well as the 24-hour urine test — which involves collecting urine passed during the day and night — for checking whether Cushing’s disease is in remission after radiotherapy, a study by U.S. researchers found.
In Cushing’s patients post-radiotherapy, late-night salivary cortisol testing, or LNSC, “appears to be clinically equivalent to UFC [the urinary free cortisol test] in the assessment of endocrine remission,” the team wrote.
Further, because saliva is easier for patients to collect at home, it may be a more convenient option for long-term monitoring, the researchers noted.
Still, given that this work was retrospective, more — and prospective — studies “are needed to confirm and extend these findings,” the team wrote.
The study, “The Role of Late-Night Salivary Cortisol in the Assessment of Endocrine Remission in Patients With Cushing’s Disease After Pituitary Radiotherapy,” was published in the journal Clinical Endocrinology.
Scant data available on test of cortisol in late-night saliva
Cushing’s disease is caused by a tumor that forms in the brain’s pituitary gland and leads to the excessive production and release of adrenocorticotropic hormone (ACTH). This hormone signals the adrenal glands, located atop the kidneys, to produce cortisol. Too much cortisol can result in weight gain, high blood pressure, and other symptoms.
The first-line treatment for Cushing’s typically is surgery to remove the pituitary tumor that’s causing the condition.
Radiotherapy, also known as radiation therapy, is often used to destroy tumor cells in patients who are not eligible for surgery. It’s also used when surgery does not fully remove the tumor, or if the disease recurs.
After radiotherapy, doctors need to check if the treatment has worked and whether cortisol levels have gone back to normal. Two possible ways to check this are the LNSC and UFC tests.
“However, there are very limited data regarding the role of LNSC in the evaluation of patients with [Cushing’s disease] who underwent [radiotherapy],” the researchers wrote.
To learn more, the team assessed and compared the outcomes of Cushing’s disease patients whose cortisol levels were monitored with either the saliva or urine test following radiotherapy.
Researchers note tests appear ‘clinically equivalent’
The study involved 75 patients from Massachusetts General Hospital who had undergone at least one surgery to remove a pituitary tumor before radiotherapy.
The patients had a median age of 50, and most (71%) were women. Among them, the average BMI, or body mass index — a ratio of weight to height used as a measure of body fat — was 34.7 kg/m2, which falls within the obesity range. Nearly two-thirds had a large pituitary tumor known as a macroadenoma.
Over a median follow-up of 56 months, or slightly longer than 4.5 years, 34 patients (45%) achieved endocrine remission. That means their cortisol levels remained within the normal range for at least three months after radiotherapy, without the use of any cortisol-lowering medication.
Those who achieved remission were divided into two groups. One group had LNSC tests, either alone (six patients) or together with UFC tests (10 patients). The other had only UFC tests (18 patients). All showed normal results at remission, and no one had conflicting LNSC and UFC results at that time.Â
When comparing the two groups, there were no differences in how long it took to achieve remission, how much BMI or blood pressure dropped, or how likely the patients were to have the disease come back. The use of medications to lower blood pressure and blood sugar levels among these individuals also was about the same.
Based on our data, LNSC [the late-night salivary cortisol test] may be used for primary response assessment of patients with [Cushing’s disease] after [radiotherapy]. … [This finding is] particularly compelling considering the ease of salivary specimen collection compared with UFC [urinary free cortisol] specimen collection.
While earlier studies have suggested that LNSC may not be as accurate in real-world as controlled clinical settings, the researchers here said the two tests appeared to be virtually equal in assessing endocrine remission.
“Based on our data, LNSC may be used for primary response assessment of patients with [Cushing’s disease] after [radiotherapy],” the researchers wrote, noting that this finding is “particularly compelling considering the ease of salivary specimen collection compared with UFC specimen collection.”
The team added: “These data suggest that LNSC may accurately identify endocrine remission in patients.”
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