Insulin hypoglycemia test in the diagnosis of subclinical Cushings syndrome
Feyza Yener Ozturk, Erdinc Erturk, Metin Guclu, Sinem Kiyici, Oguzkaan Unal & Sazi Imamoglu
Although subclinical Cushings syndrome (SCS) is an important metabolic risk factor in patients with adrenal incidentaloma, the diagnostic criteria for SCS has not been established yet. The aim of this study was to evaluate the diagnostic measures of SCS and to investigate the availability of insülin hypoglycemia test (IHT) in the diagnosis of SCS. Twenty patients with adrenal incidentaloma CT characteristics highly suggestive of benign adrenal adenoma with no overt hormonal hyperfunction were included in the study. Increase in the basal serum cortisol concentration or in the urinary cortisol excretion, absence of diurnal cortisol rhythm, insufficient suppression of cortisol with dexamethasone, decrease in the concentrations of DHEA-S or ACTH were used as diagnostic parameters for SCS. According to these parameters, patients are grouped as definite (2/20), probable (5/20) and improbable (13/20) SCS. All the patients were underwent insulin hypoglycemia test (IHT). Maximum increase in serum cortisol concentration after hypoglycemia (ΔF) was evaluated and borderline significance (P=0.053) was noticed between definite SCS and the other groups. When ΔF was compared with the other diagnostic parameters of SCS, there was significant correlation only with post 3 mg DST serum cortisol concentration (r=−0,463; P=0,04). The sensitivity and specifity of IHT in SCS was calculated 42 and 84%, respectively.
In conclusion, according to these findings sensitivity and specificity of IHT are not high enough to be used as a diagnostic test for SCS and also because of the risks, IHT is not suitable in the routine practice.