Discrepancy between ACTH and cortisol responses to insulin induced hypoglycaemia

Area of Science:

• Endocrinology
• Human Physiology

Background:

• The hypothalamic-pituitary-adrenal (HPA) axis regulates the body's response to stress.
• Adrenocorticotropic hormone (ACTH) stimulates cortisol release from the adrenal cortex.
• Insulin-induced hypoglycemia is a potent stimulator of the HPA axis.

Purpose of the Study:

• To investigate the relationship between plasma ACTH and cortisol concentrations during insulin-induced hypoglycemia.
• To determine if ACTH secretion capacity exceeds adrenal cortisol production capacity under stress.

Main Methods:

• Studied 26 healthy individuals undergoing insulin-induced hypoglycemia.
• Measured peak plasma concentrations of ACTH and cortisol.
• Quantified the total amount of ACTH and cortisol secreted during the hypoglycemic period.

Main Results:

• No significant correlation was observed between plasma ACTH and cortisol values.
• ACTH responses exhibited significantly greater variability compared to cortisol responses.
• Cortisol levels demonstrated a more consistent pattern of secretion.

Conclusions:

• The findings suggest a potential over-capacity of ACTH secretion relative to the adrenal cortex's cortisol secretory capacity.
• The adrenal cortex may be a limiting factor in the HPA axis response during acute stress.
• Further research is needed to fully elucidate the dynamics of ACTH-cortisol relationship under various physiological conditions.