Pathophysiology of Diabetes mellitus
Insulin is the principal hormone that regulates the uptake
of glucose from the blood into most cells of the body, especially liver,
adipose tissue and muscle, except smooth muscle, in which insulin acts via the
IGF-1. Therefore, deficiency of insulin or the insensitivity of its receptors
plays a central role in all forms of diabetes mellitus.
of glucose from the blood into most cells of the body, especially liver,
adipose tissue and muscle, except smooth muscle, in which insulin acts via the
IGF-1. Therefore, deficiency of insulin or the insensitivity of its receptors
plays a central role in all forms of diabetes mellitus.
The body obtains glucose from three main places: the
intestinal absorption of food; the breakdown of glycogen, the storage form of
glucose found in the liver; and gluconeogenesis, the generation of glucose from
non-carbohydrate substrates in the body. Insulin plays a critical role in
balancing glucose levels in the body. Insulin can inhibit the breakdown of
glycogen or the process of gluconeogenesis, it can stimulate the transport of
glucose into fat and muscle cells, and it can stimulate the storage of glucose
in the form of glycogen.
intestinal absorption of food; the breakdown of glycogen, the storage form of
glucose found in the liver; and gluconeogenesis, the generation of glucose from
non-carbohydrate substrates in the body. Insulin plays a critical role in
balancing glucose levels in the body. Insulin can inhibit the breakdown of
glycogen or the process of gluconeogenesis, it can stimulate the transport of
glucose into fat and muscle cells, and it can stimulate the storage of glucose
in the form of glycogen.
Insulin is released into the blood by beta cells (β-cells),
found in the islets of Langerhans in the pancreas, in response to rising levels
of blood glucose, typically after eating. Insulin is used by about two-thirds
of the body's cells to absorb glucose from the blood for use as fuel, for
conversion to other needed molecules, or for storage. Lower glucose levels
result in decreased insulin release from the beta cells and in the breakdown of
glycogen to glucose. This process is mainly controlled by the hormone glucagon,
which acts in the opposite manner to insulin.
found in the islets of Langerhans in the pancreas, in response to rising levels
of blood glucose, typically after eating. Insulin is used by about two-thirds
of the body's cells to absorb glucose from the blood for use as fuel, for
conversion to other needed molecules, or for storage. Lower glucose levels
result in decreased insulin release from the beta cells and in the breakdown of
glycogen to glucose. This process is mainly controlled by the hormone glucagon,
which acts in the opposite manner to insulin.
If the amount of insulin available is insufficient, if cells
respond poorly to the effects of insulin (insulin insensitivity or insulin
resistance), or if the insulin itself is defective, then glucose will not be
absorbed properly by the body cells that require it, and it will not be stored
appropriately in the liver and muscles. The net effect is persistently high
levels of blood glucose, poor protein synthesis, and other metabolic
derangements, such as acidosis.
respond poorly to the effects of insulin (insulin insensitivity or insulin
resistance), or if the insulin itself is defective, then glucose will not be
absorbed properly by the body cells that require it, and it will not be stored
appropriately in the liver and muscles. The net effect is persistently high
levels of blood glucose, poor protein synthesis, and other metabolic
derangements, such as acidosis.
When the glucose concentration in the blood remains high
over time, the kidneys will reach a threshold of reabsorption, and glucose will
be excreted in the urine (glycosuria). This increases the osmotic pressure of
the urine and inhibits reabsorption of water by the kidney, resulting in
increased urine production (polyuria) and increased fluid loss. Lost blood
volume will be replaced osmotically from water held in body cells and other
body compartments, causing dehydration and increased thirst (polydipsia).
over time, the kidneys will reach a threshold of reabsorption, and glucose will
be excreted in the urine (glycosuria). This increases the osmotic pressure of
the urine and inhibits reabsorption of water by the kidney, resulting in
increased urine production (polyuria) and increased fluid loss. Lost blood
volume will be replaced osmotically from water held in body cells and other
body compartments, causing dehydration and increased thirst (polydipsia).
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