Relevance of Screening Subclinical Cushing’s Syndrome in Patients with Type 2 Diabetes Mellitus | Chapter 4| Medical Science: Updates and Prospects Vol. 4

 

Background: Subclinical Cushing’s syndrome (SCS) is defined as autonomous cortisol secretion in patients devoid of specific clinical symptoms of hypercortisolism, as in the classic CS. Subtle cortisol hypersecretion from adrenal incidentalomas is associated with alterations of the hypothalamic-pituitary-adrenal (HPA) axis due to autonomous adrenal function, occurring in the absence of the typical clinical phenotype of hypercortisolism. This condition has been defined as subclinical Cushing’s syndrome (SCS). Despite the absence of overt symptoms, sustained exposure to chronic, slightly elevated cortisol concentrations may result in some classical metabolic complications of CS, such as impaired glucose tolerance and diabetes. Studies reported a higher frequency of SCS in type 2 diabetics, which can be considered an exacerbating factor for diabetes and poor glycemic control. Currently, the frequency of SCS is widely variable.

 

Aim of the Study: This study intends to prospectively evaluate the prevalence of SCS among type 2 diabetic (T2D) patients with poor control, and to determine whether systematic screening for SCS in T2D patients is worthwhile.

 

Methods: It was a cross-sectional study including 221 T2D patients referred to the National Institute of Nutrition of Tunis for poor glycemic control (HbA1c ≥ 8%). Inclusion criteria were age >40 years and poor glycemic control; patients with a history of adrenal mass or pituitary adenoma were excluded. SCS screening was performed in two steps. The first screening step of SCS was the 1-mg overnight dexamethasone suppression test (ODST) using a revised criterion for cortisol suppression. In the second confirmatory step, patients with abnormal ODST underwent a 48-h, 2-mg low-dose dexamethasone suppression test (LDDST) to confirm the diagnosis. The cut-off for cortisol suppression was 50 nmol/L (1.8 µmol/dL) in the two tests.

 

Results: The mean age ± SD of the patients was 58.7 ± 8.78 years. Overweight and obesity were found in 34% and 47%, respectively. Mean duration of diabetes was 10.84 ± 6.55 years, and mean baseline HbA1c ± SD was 10.9±1.8%. Thirteen patients (5.9%) failed to suppress cortisol levels less than the cut-off after ODST. SCS was confirmed by LDDST in one patient among them (0.45%). The autonomous cortisol secretion was related to a pituitary adenoma. This study revealed that the frequency of SCS of 0.45% did not allow for performing an analytical study in order to identify predictive factors of SCS among T2D patients.

 

Conclusion: SCS is rare among T2D patients. Systematic screening of SCS in T2D patients with poor glycemic control is not worthwhile. The screening should be performed only in patients with specific clinical and/or biological indicators. Further multicenter studies with larger sample sizes are needed to explore potential risk factors for SCS in T2D patients.

 

 

Author(s) Details

Manel Jemel Hadiji

Department of Endocrinology, National Institute of Nutrition, Tunis, Tunisia.

 

Imen Ksira
Department of Endocrinology, National Institute of Nutrition, Tunis, Tunisia.

 

Emna Haouat
Department of Endocrinology, National Institute of Nutrition, Tunis, Tunisia.

 

Henda Kammoun Jamoussi
Department of Nutrition, National Institute of Nutrition, Tunis, Tunisia.

 

Hajer Kandara
Department of Endocrinology, National Institute of Nutrition, Tunis, Tunisia.

 

Ines Kammoun
Department of Endocrinology, National Institute of Nutrition, Tunis, Tunisia.

 

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