Is biochemical hypoglycemia necessary during an insulin tolerance test?

Area of Science:

• Endocrinology
• Clinical Medicine

Background:

• The insulin tolerance test (ITT) is the gold standard for assessing the integrity of the growth hormone (GH)-insulin-1 growth factor (IGF-1) axis and the hypothalamic-pituitary-adrenal (HPA) axis.
• Effective ITT requires achieving biochemical hypoglycemia (blood glucose ≤ 40 mg/dL) to accurately evaluate the HPA and GH-IGF-1 axes.

Purpose of the Study:

• To compare the growth hormone (GH) and cortisol responses in patients who achieved biochemical hypoglycemia versus those who did not during an insulin tolerance test (ITT).

Main Methods:

• One hundred thirty-five patients with pituitary disorders were included.
• Patients were categorized into hypoglycemic (plasma glucose ≤ 40 mg/dL) and nonhypoglycemic (plasma glucose > 40 mg/dL) groups based on blood glucose levels after clinical hypoglycemia symptoms appeared during ITT.
• GH and cortisol responses were compared between the two groups.

Main Results:

• No statistically significant differences were observed in peak GH and cortisol responses between the hypoglycemic and nonhypoglycemic groups.
• The mean blood glucose level was significantly lower in the hypoglycemic group (19.3 mg/dL) compared to the nonhypoglycemic group (52.0 mg/dL).
• Patient demographics including age, BMI, and waist circumference were similar between the groups.

Conclusions:

• Clinically symptomatic hypoglycemia during an ITT appears to be as effective as biochemically confirmed hypoglycemia for assessing the GH-IGF-1 and HPA axes.
• This finding may simplify the ITT procedure and interpretation in clinical practice.