Glycemia or glycæmia is the concentration of glucose in the blood. It is usually expressed in milligrams per deciliter (mg/dl) in the US and other countries. It may also be expressed in millimol per decilitre (mmol/dl) especially in Europe. Both of these are SI units. It is one of the most important controlled variables in the internal milieu of animals (homeostasis), as it was first proposed by French physiologist Claude Bernard (1813-1878).
Glycemia is controlled by several physiological processes. It tends to fluctuate to higher levels after meals, due to the gastric and intestinal absorption of carbohydrates of low molecular weight present in the diet or broken down from other kinds of foodstuffs, such as starches (polysaccharides), and to lower levels with usage by catabolism, particularly after stress, temperature regulation and physical exertion. Another input to glycemia levels is gluconeogenesis, whereby glycogen stored in the liver or amino acids and lipids are converted to glucose via several metabolic chains. Excess glucose is converted to glycogen or to triglycerides for energy storage.
Glucose is the most important source of metabolic energy for the majority of cells, particularly for some cells (e.g., neurons and erythrocytes) which are almost totally dependent on it. The brain requires a fairly stable glycemia in order to function normally. Concentrations of less than about 30 mg/dl or greater than about 300 mg/dl can produce confusion, unconsciousness and convulsions.
Several hormones are involved in the regulation of glucose metabolism, such as insulin, glucagon (secreted by the pancreas), epinephrine (adrenaline secreted by the adrenal glands), glucocorticoids and steroid hormones (secreted by the gonads and adrenal glands).
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