REGULATION OF BLOOD GLUCOSE
The maintenance of glucose level in blood within narrow limits is a very finely and efficiently
regulated system.
This is important, because it is essential to have continuous supply of glucose to the brain. Even
though it can utilize ketone bodies to some extent, brain has an obligatory requirement for glucose.
RBC and renal medulla are also dependent on glucose for meeting their fuel needs.
Post-prandial Regulation
Following a meal, glucose is absorbed from the intestine and enters the blood.
The rise in the blood glucose level stimulates the secretion of insulin by beta cells of islets of
Langerhans of pancreas.
The uptake of glucose by most extrahepatic tissues, except brain is not dependent on insulin.
Moreover, insulin helps in the storage of glucose as glycogen or its conversion to fat.
Factors Maintaining Blood Sugar
The plasma glucose level at an instant depends on the balance between glucose entering and leaving
the extracellular fluid.
2. Hormones will make this balance possible (Fig. 24.1).
3. The major factors which cause entry of glucose into blood are:
a. Absorption from intestines
b. Glycogenolysis (breakdown of glycogen)
c. Gluconeogenesis
d. Hyperglycemic hormones (glucagon, steroids)
4. Factors leading to depletion of glucose in blood are:
a. Utilization by tissues for energy -glycolysis
b. Glycogen synthesis
c. Conversion of glucose into fat (lipogenesis)
d. Hypoglycemic hormone (insulin).
Regulation in Fasting State
i.Normally, 2 to 2½ hours after a meal, the blood glucose level falls to near fasting levels. It may go
down further; but this is prevented by processes that contribute glucose to the blood.
ii.For another 3 hours, hepatic glycogenolysis will take care of the blood glucose level.
iii. Thereafter, gluconeogenesis (Figs 24.2A and B).will take charge of the situation.
iv. Liver is the major organ that supplies the glucose for maintaining blood glucose level (Fig. 24.1).
v. Hormones like glucagon, epinephrine, glucocorticoids, growth hormone, ACTH and thyroxine
will keep the blood glucose level from falling. They are referred to as antiinsulin hormones or
hyperglycemic hormones. An overview of the regulatory mechanism is shown in Figure 24.3.
Effects of hormones are shown in Box 24.2
.A. Effect of Insulin (hypoglycemic hormone)
1.Lowers blood glucose
2.Favors glycogen synthesis
3.Promotes glycolysis
4.Inhibits gluconeogenesis
B. Glucagon (hyperglycemic hormone)
1.Increases blood glucose
2.Promotes glycogenolysis
3.Enhances gluconeogenesis
4.Depresses glycogen synthesis
2. Increases gluconeogenesis
3. Releases amino acids from the muscle
D. Epinephrine or Adrenaline (hyperglycemic)
1. Increases blood glucose level
2. Promotes glycogenolysis
3. Increases gluconeogenesis
4. Favors uptake of amino acids
E. Growth Hormone
Effects of Hormones on Glucose Level in Blood.