The size of adrenal incidentalomas correlates with insulin resistance. Is there a cause-effect relationship?
BACKGROUND
Adrenal incidentalomas (AI) have often been associated with a high prevalence of insulin resistance (IR) and cardiovascular risk factors, although direct measurement of insulin sensitivity (IS) has never been carried out.


OBJECTIVE
We aimed to investigate whether the morphological and hormonal features of AI correlate with the presence and severity of IR, using the hyperinsulinaemic euglycaemic clamp (HEC).


METHODS
Forty patients with AI (22 women) with a mean age of 58.5±11.1 years underwent hormonal and morphological evaluation. Nineteen patients with AI without known history of diabetes mellitus (DM) or impaired glucose tolerance (IGT) and 17 matched controls underwent oral glucose tolerance test (OGTT) and hyperinsulinaemic euglycaemic clamp (HEC).


RESULTS
Diabetes mellitus was observed in 13 patients (33%), while three (8%) had IGT. Thirty-one of the AI were nonfunctioning (82.5%), whereas two (5%) secreted cortisol (Cushing's syndrome) and seven (12.5%) showed subclinical secretion of cortisol. The 19 patients with nonfunctioning AI were more insulin resistant than controls (glucose up-take: 4.58±1.80 vs 5.85±2.48 mg/kg/min respectively; P=0.01); IS was inversely related to the mass size (r=-0.57; P=0.04), free urinary cortisol (r=-0.68; P=0.01), serum cortisol after 1-mg dexamethasone suppression (-0.65; P=0.02) and percentage of trunk fat mass (-0.77; P=0.02) and directly related to serum adreno cortico tropic hormone (ACTH) (r=0.62; P=0.03). After performing multivariate regression, the mass size was found to be the most powerful predictor of IR.


CONCLUSIONS
Our study showed a high prevalence of insulin resistance in patients with nonfunctioning AI and suggests its possible involvement in AI growth.
Endocrinology and Metabolic Diseases, Catholic University-Policlinico A. Gemelli, Largo A. Gemelli 8, 00168 Rome, Italy. giovanna.muscogiuri@edu.rm.unicatt.it
Giovanna
G
Muscogiuri
Gian Pio
GP
Sorice
Annamaria
A
Prioletta
Teresa
T
Mezza
Clelia
C
Cipolla
Enrica
E
Salomone
Andrea
A
Giaccari
Alfredo
A
Pontecorvi
Silvia
S
Della Casa
D000310:Adrenal Gland Neoplasms / Q000097:blood / Q000473:pathology; D000368:Aged; D003920:Diabetes Mellitus / Q000175:diagnosis; D005260:Female; D015309:Glucose Clamp Technique; D005951:Glucose Tolerance Test; D006801:Humans; D006854:Hydrocortisone / Q000097:blood / Q000652:urine; D007333:Insulin Resistance; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D012044:Regression Analysis
D006854:Hydrocortisone