Is biochemical hypoglycemia necessary during an insulin tolerance test?

ABSTRACT Objective The insulin tolerance test (ITT) has been accepted as the gold standard test for assessing the integrity of the growth hormone (GH) – insulin-like growth factor (IGF-1) axis and the hypothalamic-pituitary-adrenal (HPA) axis. The goal of the test is to achieve clinical and biochemical hypoglycemia at a blood glucose level ≤ 40 mg/dL to effectively and correctly assess the HPA and GH-IGF-1 axes. In this study, the GH and cortisol responses of patients who achieved and failed to achieve biochemical hypoglycemia during an ITT were compared. Subjects and methods One hundred thirty-five patients with pituitary disorders were included in the study. Samples for blood glucose levels were obtained after clear symptoms of clinical hypoglycemia developed. The patients were enrolled in the hypoglycemic and nonhypoglycemic groups according to whether their plasma glucose level ≤ 40 mg/dL or > 40 mg/dL during an ITT, and the groups were compared in terms of their GH and cortisol responses. Results The mean age, body mass index and waist circumference of the two patient groups were found to be similar. The mean blood glucose level was significantly lower in the hypoglycemic group than in the nonhypoglycemic group (19.3 and 52.0 mg/dL, respectively). When the two groups were compared in terms of peak cortisol and GH responses, no statistically significant differences were found. Conclusion The data presented suggest that clinically symptomatic hypoglycemia is as effective as biochemically confirmed hypoglycemia during an ITT. Arch Endocrinol Metab. 2020;64(1):82-8

摘要
研究目的：胰岛素耐量试验（Insulin Tolerance Test, ITT）已被公认为评估生长激素（Growth Hormone, GH）-胰岛素样生长因子（Insulin-like Growth Factor, IGF-1）轴与下丘脑-垂体-肾上腺（Hypothalamic-Pituitary-Adrenal, HPA）轴完整性的金标准检测方法。该检测的目标是使受试者血糖降至≤40 mg/dL，以达成临床与生化层面的低血糖状态，从而精准有效地评估HPA轴与GH-IGF-1轴的功能完整性。本研究对比了在ITT过程中达到与未达到生化低血糖标准的患者的生长激素与皮质醇应答水平。
研究对象与方法：本研究纳入135例垂体疾病患者。在患者出现明确临床低血糖症状后采集血糖样本。根据ITT实施过程中血浆葡萄糖水平是否≤40 mg/dL或＞40 mg/dL，将患者划分为低血糖组与非低血糖组，并比较两组的生长激素与皮质醇应答情况。
结果：两组患者的平均年龄、体质量指数及腰围均无显著差异。低血糖组的平均血糖水平显著低于非低血糖组（分别为19.3 mg/dL与52.0 mg/dL）。对比两组的皮质醇与生长激素峰值应答水平，未发现统计学显著性差异。
结论：本研究数据表明，在ITT中，临床症状性低血糖与经生化证实的低血糖具有同等的评估效能。
《内分泌代谢档案（Arch Endocrinol Metab）》2020;64(1):82-8