is a hormone, produced by the pancreas, which is central
to regulating carbohydrate and fat metabolism in the body.
Insulin causes cells in the liver, muscle, and fat tissue
to take up glucose from the blood, storing it as glycogen
inside these tissues. Insulin stops the use
of fat as an energy source by inhibiting the release of
glucagon. With the exception of the metabolic disorder diabetes
mellitus and metabolic syndrome, insulin is provided within
the body in a constant proportion to remove excess glucose
from the blood, which otherwise would be toxic. When blood
glucose levels fall below a certain level, the body begins
to use stored sugar as an energy source through glycogenolysis,
which breaks down the glycogen stored in the liver and muscles
into glucose, which can then be utilized as an energy source.
As a central metabolic control mechanism, its status is
also used as a control signal to other body systems (such
as amino acid uptake by body cells). In addition, it has
several other anabolic effects throughout the body."