The blood glucose level is tightly regulated between 70-110 mg/dl. After eating, levels may rise to 120-140 mg/dl before returning to normal. The liver plays a key role in regulating glucose through metabolic processes and hormones like insulin and glucagon. Insulin promotes glucose uptake and storage after eating, while glucagon and other hormones like epinephrine release glucose into the blood during periods of low blood sugar. Together, these hormonal and organ responses help maintain blood glucose within a narrow range.

1. BLOOD GLUCOSE LEVEL AND ITS
REGULATION

2. • The blood glucose level must be maintained
within the narrow limits of 70-110mg/dl.
• Levels above the normal range are called
hyperglycemia and those below are called
hypoglycemia.
• After the ingestion of a carbohydrate meal, it
may rise to 120-140mg/dl.

3. • Factors involved in the regulation of blood
glucose are hormones, metabolic processes
and renal mechanism.
• The liver is the primarily responsible for
controlling the concentration of glucose in the
blood.
• The two major hormones controlling blood
glucose levels are
1. Insulin
2. glucagon

6. • There is an increased blood glucose level shortly
after each meal, a postprandial hyperglycemia.
• Increased level of blood glucose releases insulin
by β-cells of the islets of langerhans.
• By stimulating the active transport of glucose
across cell membrane of muscles and adipose
tissue but not the liver. Glucose is rapidly taken
up into liver as it is freely permeable to glucose.

7. • In adipose tissue, glucose is converted to the
glycerol-3-phosphate, needed for the
formation of triacylglycerol (lipogenesis).
• In the liver, insulin increases the use of
glucose by glycolysis by inducing the synthesis
of key glycolytic enzymes.
• In the muscles and liver, insulin stimulates
glycogenesis by stimulating glycogen synthase
and leading to the suppression of
glycogenolysis.

8. • Insulin inhibits gluconeogenesis by
suppressing the action of key enzymes of
gluconegenesis.
• I adipose tissue, glucose is converted to the
glycerol-3-phosphate, needed for the
formation of triacylglycerol.
• Insulin increases protein synthesis and
decreases protein catabolism, thereby
releasing amino acids. All these mechanisms
are responsible for a drop in blood glucose
level.

10. Decreased level of blood glucose causes a
release of hyperglycemic hormones, e.g.
• Glucagon
• Epinephrine or adrenaline
• Glucocorticoids
• Growth hormones
• thyroxin

11. • Glucagon is the hormone produced by the α-
cells of the islets of langerhans of the
pancreas.
• In the liver, it stimulates glycogenolysis by
activating enzyme glycogen phosphorylase
and inhibits glycogen synthase.
• Glucagon enhances gluconeogenesis from
amino acids and lactate by inducing the action
of key enzymes of gluconeogenesis.

12. • It is secreted by thyroid glands.
• Thyroxin accelerates hepatic glycogenolysis
with rise in blood glucose.
• It may also increase the rate of absorption of
hexoses from the intestine.

13. • It is secreted by adrenal medulla.
• It stimulates glycogenolysis in the liver and the
muscle by stimulating glycogen phosphorylase
activity via cAMP.
• In muscle as a result of the absence of
glucose-6-phosphatase, glycogenolysis results
with the formation of lactate, whereas in the
liver, glucose is the main product, leading to
increase in blood glucose.

14. • These hormones are secreted by adrenal cortex,
which causes increased:
1. Gluconeogenesis by increasing the activity of
enzymes of gluconeogenesis.
2. Protein catabolism to provide glycogenic amino
acid for gluconeogenesis.
• Glucocorticoids inhibit the utilization of glucose
in extra hepatic tissues. All the actions of
glucocorticoids are antagonistic to insulin.

16. • When blood glucose rises to high levels, the
kidney also exerts a regulatory effect.
• Glucose is continuously filtered by the
glomeruli but is normally reabsorbed
completely in renal tubules.
• If the blood glucose level is raised above
180mg/100ml, complete tubular reabsorption
of glucose doesn't occur and the extra amount
appears in the urine causing glycosuria.

17. • 180mg/ 100ml is the limiting level of glucose
in the blood, above which tubular
reabsorption does not occur which is known
as renal threshold value for glucose.
• Thus, by excreting extra amount of sugar in
the urine during hyperglycemic state and
reabsorbing sugar during the hypoglycemic
state, the kidney helps in the regulating the
level of glucose in blood.