Endocrine Abstracts

One-hour (1 h) glucose level of the oral glucose tolerance test (OGTT) was proven to be a better predictor of insulin resistance (IR) in nondiabetic population than the two-hour (2 h) postload glucose level. Specifically, the 8.6 mmol/l cut-off was shown to be an early marker of impaired glucose tolerance (IGT). Previous studies have shown that nondiabetic patients with adrenal incidentalomas (AI) have higher IR than healthy control (HC). However, despite the subtle cortisol secretion, there was no significant difference in the 2 h OGTT glucose level between patients with AI and autonomous cortisol secretion and nonfunctional AI (NAI). The aim of this study was to examine the value of 1h OGTT glucose level as an indicator of IR in AI patients. 105 nondiabetic subjects were drawn from a series of patients with AI. The AI subjects - 33 NAI and 72 with (possible) autonomous cortisol secretion (P)ACS) were age-, sex- and body mass index (BMI)-matched with 34 HC. We have evaluated OGTT, homeostasis model assessment (HOMA-IR) and index of whole-body insulin sensitivity (ISI-composite). AI patients had significantly higher 1h glucose level than HC (8.2±2.5 vs 7.1±2.2 mmol/l, P=0.021) and patients with (P)ACS had significantly higher 1 h glucose level than NAI (8.5±2.6 vs 7.3±1.98 mmol/l, P=0.002). There was no difference in 2h glucose level between AI and HC nor between NAI and (PACS). Also, there was no difference in number of patients with IGT between patients with NAI (26/7) and (P)ACS (50/22). In patients with (P)ACS there was a significant, positive correlation between the 1 h glucose level and cortisol after 1mg dexamethasone suppression test (1 mg DST) (r=.278, P=0.018) whereas there was no correlation between the 2 h glucose level and 1mg DST cortisol. Furthermore, we have divided patients with NAI and (P)ACS in: A– 1 h glucose >8.6 mmol/l and B – 1 h glucose <8.6 mmol/l. In both NAI and (P)ACS, A group had significantly lower ISI-composite than B (NAI: P=0.03, (P)ACS: P=0.03), and significantly higher HOMA-IR (NAI: P=0.05, (P)ACS: P=0.038). In patients with AI, 1h OGTT glucose level is a valuable indicator of IR. Moreover, in patients with (P)ACS, 1h OGTT glucose level seems to be a better indicator of the subtle cortisol secretion than the 2h OGTT glucose level.