Visceral Fat Accumulation and Postdexamethasone Serum Cortisol Levels in Patients With Adrenal Incidentaloma

Visceral fat is a significant cardiovascular risk factor. Because visceral fat has not been measured systematically in patients with adrenal incidentalomas, we have tested the hypothesis that visceral fat volume may be associated with cutoffs for serum cortisol levels post dexamethasone. This was a retrospective, cross-sectional study. The study was conducted at the Endocrine Investigation Unit, University Teaching Hospital. Seventy-three women and 52 men diagnosed with adrenal incidentalomas and 9 patients with overt Cushing's syndrome participated in this study. The following was measured for serum cortisol level after dexamethasone suppression and visceral fat ratios: visceral-subcutaneous (V:S) and visceral-total volume (V:TV) measured by computed tomography. Sixty-eight patients with a postdexamethasone serum cortisol greater than 1.8 μg/dL (50 nmol/L) showed a significantly higher mean V:S and V:TV fat ratio compared with those whose serum cortisol was less than 1.8 μg/dL: women, lnV:S, −0.45 vs −0.69 [mean difference 0.24 (95% confidence interval [CI] 0.08–0.41); P = .004] and V:TV, 0.39 vs 0.34 [mean difference 0.05 (95% CI 0.02–0.09); P = .004]; men, lnV:S, 0.64 vs 0.29 [mean difference 0.35 95% CI 0.08–0.63); P = .01] and V:TV, 0.65 vs 0.57 [mean difference 0.08 (95% CI 0.02–0.14); P = .02]. By ANOVA and post hoc analysis (Fisher's least significant differences), there was no difference in fat ratios between the postdexamethasone serum cortisol groups [1.8–2.9 μg/dL (50–82 nmol/L), 3.0–5.0 μg/dL (83–137 nmol/L), > 5.0 μg/dL (>138 nmol/L) and Cushing's syndrome (mean V:TV: 0.38, 0.40, 0.40, 0.41, respectively)], but they all differed significantly from the less than the 1.8-μg/dL group (V:TV: 0.34, P = .03). Visceral fat is increased in patients with adrenal incidentalomas and a postdexamethasone serum cortisol of greater than 1.8 μg/dL and is similar to that found in patients with overt Cushing's syndrome.