ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

Endocrine Abstracts (2008) 16 P4

Might the response of cortisol to oral glucose tolerance test be used for the differential diagnosis of Cushing's syndrome and pseudo-Cushing's states?

Maria Cristina De Martino, Monica De Leo, Arantzazu Sebastian Ochoa, Renata Simona Auriemma, Mariano Galdiero, Gaetano Lombardi, Annamaria Colao & Rosario Pivonello

Department of Molecular and Clinical Endocrinology ‘Federico II’ University, Naples, Italy.

The pseudo-Cushing states (PCS) include several clinical conditions such as obesity, polycystic ovary syndrome, depression and alcoholism, characterized by physical features and abnormalities of hypothalamus–pituitary–adrenal axis similar to Cushing’s syndrome (CS). The differential diagnosis between CS and PCS is often complicated and requires several hormonal tests. The aim of this study is to evaluate the diagnostic accuracy of the cortisol response to the oral glucose tolerance test (OGTT) as a screening test to distinguish patients with PCS and CS. Twenty-six patients with CS (19 females, 7 males, 18–64 years) and 26 patients with PCS (21 females, 5 males; 18–63 years) entered the study. The clinical diagnosis of CS and PC were performed on the basis of urinary cortisol, serum cortisol circadian rhythm, low dose dexamethasone suppression test (LDDST), desmopressin test and/or CRH test after LDDST. The clinical diagnosis of PCS was confirmed by the clinical follow-up of the patients, which did not develop CS during the following 5 years. All patients were submitted to OGTT: serum cortisol levels were evaluated every 30 min for 2 h. Basal serum cortisol levels were significantly higher in CD than PCS (207.3±49.9 vs 166.3±56.5 ng/ml P<0.001). Cortisol nadir was significantly higher (157.9±49.2 vs 67.6±28.9 ng/ml P<0.001) whereas cortisol decrease percentage (22.9±19.5 vs 57.6±15.8% P<0.001) was significantly lower in patients with CS than in patients with PCS. Moreover, ROC analysis showed that a cut-off of cortisol nadir of 94.4 ng/ml was able to differentiate PCS from CD with 92% sensitivity and 89% specificity, and a cut-off of 60’ after-OGTT-cortisol of 147.5 ng/ml was able to differentiate PCS from CD with 92% sensitivity and 92% specificity. These preliminary results suggest that OGTT might be considered as a valid screening test in the differential diagnosis of CS and PCS, taking into consideration that it is a simple test commonly used in the clinical practise to evaluate the glucose tolerance in patients with hypercortisolism, and with the only limitation for patients with diabetes mellitus. However, an extension of this study to a larger number of patients and the comparison of the diagnostic accuracy of OGTT and classical tests are mandatory to draw definitive conclusion of the usefulness of this test in the differential diagnosis of CS and PCS.