Endocrine Abstracts

Introduction: The insulin tolerance test (ITT) is the gold standard for hypothalamic-pituitray adrenal axis assessment. An adequate response of serum cortisol level above or equal to 18 μg/dl confirms the integrity of the adrenal axis. Otherwise, it confirms adrenal insufficiency (AI). The aim of our study was to investigate clinical and biological factors for the prediction of an adequate response during the ITT.

Methods: We conducted a cross-sectional descriptive study. It involved 100 patients with suspected AI. The ITT protocol consisted of blood samples for fasting blood glucose and baseline cortisol, followed by intravenous injection of rapid insulin at a dose of 0.1 to 0.2 IU/kg. A second sample was taken at the time of hypoglycemia, followed by blood samples every 10 minutes for 60 minutes after hypoglycemia. An adequate response was defined as a serum cortisol level above or equal to 18 μg/dl after a serum glucose level below 0.40 g/l.

Results: The mean age was 41.4±15.12 years and the gender ratio (F/H) was 0.2. Forty-two patients (42%) had an adequate response and 58 patients (58%) had an inadequate response. There was no difference of the mean age between the two groups (P=0.94). Anorexia and orthostatic hypotension were more frequent in patients with AI. (P=0.028; P<10^-3). Weight and BMI were comparable between the two groups. Fasting blood glucose and nadir blood glucose were comparable between the two groups (0.91±0.14 g/l vs 0.92±0.14 g/l; P=0.91) and (0.29±0.01 g/l vs 0.29±0.01 g/l; P=0.84). Basal cortisol level in the group with normal axis were significantly higher than in the AI group (11±4.1 µg/dl vs 8.3±2.4 µg/dl; P<0.001). A basal cortisol of 9.75 μg/dl had a sensitivity of 59% and a specificity of 73% to predict an adequate response. On the other hand, a cutoff point of 13.3 µg/dl had a sensitivity of 100% but a specificity of 26%.

Conclusions: Dynamic test is required to assess the integrity of the adrenal axis. Our study suggests that a basal cortisol of 9.75 µg/dl reliably predicts adequate cortisol response.