Insulin

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Insulin is a protein hormone secreted by the Beta Cells of the Islets of the Langerhans within the pancreas, an endocrine gland in the human body.

Insulin is extremely important for the regulation of the amount of sugar (glucose) in the blood.

The secretion of insulin by the Beta Cells of the pancreas is stimulated by (high) concentration of blood sugar. The insulin secreted prevents the amount of sugar in the blood from rising to a dangerous level by acting in many ways, including:

• Easing and increasing the rate of diffusion of glucose from the blood into most of the body cells - especially the skeletal muscle fibers.
• Accelerating the conversion of glucose into glycogen and fatty acids.
• Promoting the uptake of amino acids into body cells and increasing the production of proteins within cells.
• Reducing the rate of conversion of liver glycogen into glucose.
• Reducing the rate of formation of glucose by liver cells.

Conversely, when blood sugar levels fall to below the typically "normal" level i.e. in the range 4-10 m.mol/litre, another hormone called glucagon increases the quantity of glucose in the blood.

Insufficient or "hypo-" insulin gives rise to diabetes mellitus. Symptoms include:

• Blood glucose levels rising (hyperglycaemia)
• Glucose excreted into the urine (glycosuria),
• ... which increases levels of urination, causing dehydration.
• As glucose levels in the blood increase, fat and protein are broken-down for energy.

Coma and death may follow if the symptoms of a diabetes mellitus hypo- insulin situation are not treated.

See also: What is a Hormone ?

For further general information including the locations of the endocrine glands, see the Endocrine Glands of the Human Body.