Subclinical Cushing's syndrome in adrenal incidentalomas--possible metabolic consequences

The presence of subclinical Cushing's syndrome (SCS) and some features of the metabolic syndrome were evaluated in adrenal incidentaloma patients.

165 patients were studied. Plasma cortisol, ACTH, DHEA-S, 17-OH-P, aldosterone, renin activity and 24-h urinary methoxycatecholamines were measured. Fasting concentrations of glucose, insulin, triglycerides, T-chol., HDL-chol. and LDL-chol. were determined and the FIRI and QUICKI indices were calculated. Blood pressure, WHR and BMI were determined in all patients. Forty healthy volunteers were the controls.

133 patients had unchanged endocrine function, 32 demonstrated hormonal disturbances without clinical symptoms (in 26 nonclinical hypercortisolism). The WHR and blood pressure in the SCS group were significantly higher than in the patients with nonfunctioning adenoma (NA). T-chol and LDL-chol were significantly higher, but HDL-chol was significantly lower, in the SCS than in the NA patients. Fasting insulin level was significantly higher in the SCS than in the NA patients and controls, while fasting glucose level was comparable. QUICKI was significantly lower in the SCS and NA patients than in the controls, while FIRI was significantly higher in the SCS group.

In incidentaloma patients, hormonal function of the adrenal gland should be estimated because some of them present subclinical hyperfunction. These patients frequently display features of metabolic syndrome such as insulin resistance, hypertension, high triglycerides, T-chol and LDL-chol levels. Subtle autonomous cortisol secretion may be the cause of these features.