Do patients with type 2 diabetes mellitus have an increased prevalence of Cushing's syndrome?

Abstract

Many clinical features are common for patients with type 2 diabetes mellitus (T2DM) and Cushing's syndrome (CS) such as central obesity, hypertension and dyslipidaemia. Patients with CS often have T2DM. Because T2DM is much more frequent than CS, it is possible that some patients with T2DM have increased production of cortisol and thus represent patients with CS. The aim of this review was to evaluate the prevalence of CS in patients with T2DM. A search was performed in PubMed and Medline. We found seven prospective studies, two case-control studies and two cross-sectional studies. The difficulties in diagnosing subclinical CS is discussed. The most frequent tests for diagnosing CS, late-night salivary cortisol, 1-mg dexamethasone suppression test and urinary free cortisol are discussed and put in relation to the results of the literature found. The observed prevalence of CS in patients with T2DM varies widely between the different studies, ranging from 0-9.4%. This may be due to patient selection, differences in test methodology (including choice of test), cutoff values and different cortisol assays. The true prevalence of CS in T2DM has not been determined. We need more studies investigating the prevalence of CS in T2DM patients. There is a need for developing more specific tests for diagnosing CS in patients with only slightly elevated cortisol secretion and subclinical CS. We suggest that examination for hypercortisolism should only be performed in T2DM patients with a cushingoid appearance and hypertension or truncal obesity or dyslipidaemia.

DIAGNOSIS OF ENDOCRINE DISEASE: Prevalence of hypercortisolism in type 2 diabetes patients: a systematic review and meta-analysis

“…A review from 2012 recorded a wide scatter in the prevalence of CS in T2D ranging between 0 and 9.4% based on 11 studies using different biochemical criteria (9). Proper identification of such patients may have important clinical implications as CS may be curable by surgery, whereas T2D is a chronic disease requiring lifelong medical treatment.…”

DIAGNOSIS OF ENDOCRINE DISEASE: Differentiation of pathologic/neoplastic hypercortisolism (Cushing’s syndrome) from physiologic/non-neoplastic hypercortisolism (formerly known as pseudo-Cushing’s syndrome)

“…Pathologic Cushing's syndrome may be an unsuspected finding in patients with type 2 diabetes mellitus with a prevalence as high as 3% (43,44,45,46,47). The converse is also true in that patients with diabetes mellitus with poor glycemic control may have an activated HPA axis (48).…”

Is It Relevant to Screen Subclinical Cushing’s Syndrome in Patients With Type 2 Diabetes Mellitus?

“…This insulin resistance during type 2 diabetes results in a clinical expression identical to that found during SCS, making it even less obvious the diagnosis of an SCS associated with diabetes [12,23]. Thus, we performed a systematic screening of SCS in T2D patients with chronic poor glycemic control.…”