BETHESDA, MARYLAND. Cushing's syndrome is characterized by excessively high cortisol levels and symptoms such as weight gain, depression, and hypertension. Current screening tests (urine cortisol level and dexamethasone suppression screening) are only accurate to within about 30%. Researchers at the National Institutes of Health now report that measuring nighttime salivary cortisol levels can provide an accurate indication of the presence of Cushing's syndrome. The researchers studied 156 patients suspected of having Cushing's syndrome, 29 other patients known not to have the condition, and 34 healthy volunteers. They found that the nighttime (midnight) salivary cortisol levels in patients with Cushing's syndrome were invariably above 550 ng/dL (15.2 nmol/L) while non-Cushing's syndrome participants had levels at or below 220 ng/dL. The researchers conclude that nighttime salivary cortisol levels above 550 ng/dL will identify 93% of all patients that actually have Cushing's syndrome and will exclude all individuals without the disorder. They endorse the use of nighttime salivary cortisol as a simple, convenient, accurate, and cost-effective screening test for Cushing's syndrome.
Papanicolaou, Dimitris A., et al. Nighttime salivary cortisol: a useful test for the diagnosis of Cushing's syndrome. Journal of Clinical Endocrinology & Metabolism, Vol. 87, October 2002, pp. 4515-21