Type 2 diabetes (T2D) may be sustained by several endocrine diseases, in particular, overt endogenous glucocorticoid excess - Cushing’s syndrome. Although a known cause of hyperglycaemia, Cushing’s syndrome is of relatively low prevalence, making it unlikely to be a major frequent contributor to T2D. More recently, the more common subclinical hypercortisolism (SH), characterised by impaired adrenocorticotrophic hormone/cortisol homeostasis, has been suggested to increase the risk of T2D, and a high prevalence of SH has been demonstrated in T2D patients with poor metabolic control.In this first controlled study on the prevalence of SH in T2D, Chiodini and colleagues compare T2D patients and non-diabetic age- and body mass index-matched controls. Their findings show SH to be nearly 5 times more common in T2D patients than in controls, independent of obesity and hypertension – the proportion of T2D statistically attributable to SH in this population being approximately 7%. Individuals with SH tend to require insulin treatment more frequently than those without SH and have a propensity towards a more severe form of T2D characterised by the simultaneous presence of hypertension, dyslipideamia and need for insulin treatment. Chiodini et al.’s data are confirmatory of previous research suggesting that diabetics with SH are typified by poor metabolic control, with the possibility of a cause-effect relationship between SH and T2D also reinforced by evidence of reduced glycated haemoglobin in patients receiving surgical treatment for SH.

EJE 153(6) pp 845–852