Glycemia

Glycemia is the concentration of glucosein the blood. It is usually expressed in milligrams per deciliter (mg/dl). It is one of the most important controlled variables in the internal milieu of animals (homeostasis), as it was first proposed by FrenchphysiologistClaude Bernard(1813-1878).

Physiological regulation

Glycemia is controlled by several physiologicalprocesses. It tends to fluctuate to higher levels after meals, due to the gastricand intestinalabsorptionof carbohydratesof low molecular weightpresent in the dietor broken down from other kinds of foodstuffs, such as starches(polysaccharides); and to lower levels with usage by cell metabolism, particularly after stress, temperature regulationand physical exhertion. Another input to glycemia levels is neoglucogenesis, whereby glycogenstored in the liverand skeletal muscles, or aminoacidsand lipidsare converted to glucose via several metabolic chains. Excess glucose is converted to glycogen or to triglyceridesfor energy storage.

Glucose is the most important source of metabolic energy for the majority of cells, particularly for some cells (e.g., neuronsand 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, unconsciousnessand convulsions.

Several hormonesare involved in the regulation of glucose metabolism, such as insulin, glucagon(secreted by the pancreas), adrenalin(secreted by the adrenal glands), glucocorticoidsand steroid hormones(secreted by the gonadsand adrenal glands).

Measurement

For clinical evaluation purposes, there are two ways of measuring glycemia:

• Fasting glycemia: measured in a blood sample taken after 8 hours of complete fasting;
• Blood glucose tolerance test(OGTT): measured in several blood samples taken at intervals following a given glucose load (oral intake of endovenous injection).

In certain conditions, it is recommended that blood glucose monitoringbe performed regularly, usually by the patient himself, who is trained to do a digital venipunctureand use a small portable glucometerdevice to evaluate glycemia levels instantly.

Glycemia fluctuates physiologically within a narrow range. Excessively low levels (e.g. a fasting glycemia of 70 mg/dl or below) are classed as hypoglycemia. These may result from poor diet, or as a side effect of diabetesmedication. Excessively high levels (e.g. 250 mg/dl or more) are classed as hyperglycemiaand are a particular threat to diabetessufferers.

• 70-100 mg/dL: Normal
• 101-125 mg/dL: Impaired fasting glucose
• 126 mg/dL and above: Risk of diabetes

Abnormal values

Many forms of severe stress and trauma, stroke, heart attack, and surgerycan temporarily increase glucose levels. Glycemia can also be increased by certain drugssuch as antidepressants, corticosteroids, diuretics, estrogens, lithium, phenotiazine, phenytoinand salicilates; or decreased by others, such as acetaminophen, alcohol, steroids, clofibrate, gemfibrozil, etc.

However, the disease most directly associated to chronic increase of glycemia is diabetes mellitus, due to a decrease in the secretion of insulin, excess of its breakdown or decreased capacity of cells to transport it across its membranes(insulin resistance).

See also

• Hypoglycemia
• Hyperglycemia
• Glucose
• Diabetes

External links

• Glucose test. Medline Plus.
• Blood glucose monitoring. Medline Plus.
• Glucose tolerance test. Medline Plus.es:Glicemia

it:Glicemia pt:Glicemia

This article is licensed under the GNU Free Documentation License.
It uses material from the http://en.wikipedia.org/wiki/Glycemia Wikipedia article Glycemia.