Journal of Clinical Endocrinology & Metabolism , doi:10.1210/jc.2009-2453
K. Mullan, N. Black, A. Thiraviaraj, P. M. Bell, C. Burgess, S. J. Hunter, D. R. McCance, H. Leslie, B. Sheridan, and A. B. Atkinson*
Regional Centre for Endocrinology and Diabetes (K.M., N.B., A.T., P.M.B., S.J.H., D.R.M., A.B.A.), and Regional Endocrine Laboratory (C.B., H.L., B.S.), Royal Victoria Hospital, Belfast BT12 6BA, United Kingdom
* To whom correspondence should be addressed. E-mail: firstname.lastname@example.org..
Context: Subclinical Cushing's syndrome has been described among diabetic populations in recent years, but no consensus has emerged about the value of screening.
Methods: We enrolled 201 consecutive patients attending our diabetes clinic and 79 controls. Patients with at least two of the following three criteria were offered screening using a 2300 h salivary cortisol test: glycosylated hemoglobin of at least 7%, body mass index of at least 25 kg/m2, and a history of hypertension or blood pressure of at least 140/90 mm Hg. Results are expressed as mean ± SEM.
Results: Mean nighttime salivary cortisol levels were similar in the two groups (8.5 ± 1.0 nmol/liter for diabetic patients vs. 5.8 ± 1.0 nmol/liter for controls). Forty-seven patients (23%) had a value of at least 10 nmol/liter, which was set as a conservative threshold above which further investigation would be performed. Thirty-five (75%) agreed to further testing with a 1-mg overnight dexamethasone test. Of the remaining 12 patients, 10 were followed up clinically for at least 1 yr, and no evidence was found of the syndrome evolving. In 28 patients, serum cortisol suppressed to 60 nmol/liter or less. Of the seven patients who failed this test, four agreed to a 2 mg/d 48-h dexamethasone test, with serum cortisol suppressing to 60 nmol/liter or less in all four. Three declined this test but had normal 24-h urinary free cortisol levels. No patient had clinical features of hypercortisolism.
Conclusions: The 1–3% detection rates of three recently published series have not been realized at our center where we studied a group using criteria making patients more likely to have hypercortisolism. Our results do not support the validity of screening patients without clinical features of Cushing's syndrome in the diabetes clinic.