Endocrine Abstracts

Aims: SC can be discovered in 5–20% of the incidentalomas. Subclinical secretion is defined by the failure to suppress plasma cortisol after 1 mg-overnight dexamethasone <50 nmol/l, but there is no agreement in literature. The aim of our study was to evaluate cortisol response to oral glucose tolerance test (OGTT) as potential marker of autonomous activity of these adenomas.

Methods: Ninety subjects, 47 females and 43 males, underwent the protocol of study running in our Unit, which included clinical evaluation, basal hormonal and biochemical evaluation, OGTT, 1 mg-dexamethasone suppression test, and CT scan when not available. Primary hyperaldosteronism, hyperandrogenism, malignancy and other adrenal pathologies were excluded; subjects with type 2 diabetes were also excluded from the study.

Results: SC had significantly larger adenomas than non secreting adenomas (NSA) (P<0.005). There were no significant differences in metabolic parameters between the two groups. Glucose and insulin levels during the OGTT were not significantly different between the groups. There were no significant differences in the prevalence of metabolic syndrome between the two groups. Cortisol_OGTT-tAUC were significantly higher in SC than in NSA (P<0.05). Glucose_OGTT-tAUC were higher in SC than in NSA, even though this difference did not reach the statistical significance (P=0.058). OGTT-tAUC were similar between the two groups.

Post-dexamethasone cortisol (Fdex) was positively and significantly related to adenoma size (r=0.292, P<0.01) and to glucose_OGTT-tAUC (r=0.254, P<0.05). The relationship between cortisol_OGTT-tAUC and glucose_OGTT-tAUC was statistically significant in SC (t=6.86, P=0.010) but not in NSA (t=0.230, P=0.631), without any effect of gender.

Conclusions: SC showed a lower reduction of cortisol levels following oral glucose load. This finding should be red as a partial autonomic secretion by adenomas. Thus, cortisol response to OGTT should represent another element to evaluate, together with Fdex, in order to define the secretion of the adrenal mass.