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Late-night salivary cortisol accurate test for Cushing's syndrome in obesity, PCOS

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July 26, 2017

Measuring late-night salivary cortisol levels was an accurate method for diagnosing Cushing’s syndrome among women with polycystic ovary syndrome or obesity, according to researchers in Turkey.

“Late-night salivary cortisol measurement has recently gained widespread acceptance as a non-invasive, reliable and easy-to-perform test in the diagnosis of Cushing’s syndrome,” Hande Mefkure Ozkaya, MD, of the department of endocrinology and metabolism at Cerrahpasa Medical School, University of Istanbul, and colleagues wrote. “Emerging evidence suggests an increase in the hypothalamio-pituitary-adrenal axis drive in patients with obesity and polycystic ovarian syndrome. [Late-night salivary cortisol] may thus be falsely elevated in these patients, which raises the question as to whether different cutoff points should be used. Considering the current increase in the prevalence of obesity and metabolic syndrome leading to the increased number of patients in whom [Cushing’s syndrome] should be excluded, determination of cutoff points specific to these diseases has become necessary.”

The researchers collected two consecutive late-night salivary cortisol samples from 124 study women, including 25 with Cushing’s syndrome, 21 with obesity, 44 with PCOS (22 with obesity and 22 without) and 34 healthy participants (9 men).

Participants with Cushing’s syndrome showed significantly higher late-night salivary cortisol levels than healthy participants, those with obesity and those with PCOS, Ozkaya and colleagues reported (P < .01 for all). There was no significant difference in median late-night salivary cortisol levels among healthy participants, those with PCOS, or those with obesity (P > .05), and cutoff values, as well as specificity and sensitivity, were similar across groups. Furthermore, the researchers reported that there was no significant difference between male and female participants’ median late-night salivary cortisol levels (P = .12).

When researchers compared the area under the curve, they reported no significant difference between the first test (AUC, 0.963; 95% CI, 0.910-0.989) and the second (AUC, 0.954; 95% CI, 0.898-0.984), or from the mean of both tests (AUC, 0.962; 95% CI, 0.909-0.989). Among healthy participants, a median late-night salivary cortisol cutoff level of 7.45 nmol/L produced 100% sensitivity and 87.5% specificity.

Ozkaya and colleagues noted that the study was limited by the fact that they used a lower cutoff value than that provided by the manufacturer of the assay and that their analysis included only patients with “overt” Cushing’s syndrome and not those with subclinical or cyclical Cushing’s syndrome. The researchers also included men in the healthy participants group, while the PCOS and obesity groups included only women.

“In conclusion, our results suggest that [late-night salivary cortisol secretion] is a reliable test with high diagnostic accuracy in patients with PCOS and obesity; two frequent conditions that might mimic [Cushing’s syndrome] in general clinical practice.” – by Andy Polhamus

Disclosure: The researchers report no relevant financial disclosures.


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