What happens when blood glucose levels are too high or too low, and how do insulin and glucagon act to bring these levels back to normal?

SouravNovember 12, 2024

Answered step-by-step

When blood glucose levels are too high (hyperglycemia) or too low (hypoglycemia), the body experiences various physiological responses, and the hormones insulin and glucagon play critical roles in restoring balance.

High Blood Glucose Levels (Hyperglycemia)

• Causes: Hyperglycemia often occurs in individuals with diabetes, particularly when insulin production is insufficient or ineffective. It can also result from excessive carbohydrate intake, stress, illness, or hormonal imbalances.
• Symptoms: Common symptoms include increased thirst, frequent urination, fatigue, blurred vision, and headaches. If left untreated, hyperglycemia can lead to serious complications such as diabetic ketoacidosis (DKA) or hyperosmolar hyperglycemic state (HHS), both of which can be life-threatening.
• Hormonal Response:
  • Insulin Release: In response to high blood glucose levels, the pancreas secretes insulin from beta cells. Insulin facilitates the uptake of glucose by cells for energy and stimulates the liver to convert excess glucose into glycogen for storage. This process lowers blood sugar levels and helps restore homeostasis .

Low Blood Glucose Levels (Hypoglycemia)

• Causes: Hypoglycemia can occur due to excessive insulin administration (in diabetics), prolonged fasting, excessive exercise, or certain medications. It can also happen if meals are skipped or delayed.
• Symptoms: Symptoms of hypoglycemia include shakiness, sweating, irritability, confusion, dizziness, rapid heartbeat, and in severe cases, seizures or loss of consciousness .
• Hormonal Response:
  • Glucagon Release: When blood glucose levels drop too low, the pancreas releases glucagon from alpha cells. Glucagon prompts the liver to convert stored glycogen back into glucose (glycogenolysis) and stimulates gluconeogenesis (the production of glucose from non-carbohydrate sources). This process raises blood sugar levels back to normal .

Feedback Mechanism

The regulation of blood glucose levels by insulin and glucagon operates through a negative feedback loop:

• When blood sugar rises after eating, insulin is secreted to lower it.
• Conversely, when blood sugar falls between meals or during fasting, glucagon is released to increase it. This continuous cycle ensures that blood glucose levels remain within a narrow range essential for normal bodily functions