Glycemia
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2008-04-22T21:18:39Z
Chris the speller
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'''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 [[France|French]] [[physiologist]] [[Claude Bernard]] (1813-1878).
==Physiological regulation==
Glycemia is controlled by several [[physiology|physiological]] processes. It tends to fluctuate to higher levels after meals, due to the [[stomach|gastric]] and [[intestinal]] [[absorption (digestive)|absorption]] of [[carbohydrate]]s of low [[molecular weight]] present in the [[Diet (nutrition)|diet]] or broken down from other kinds of [[foodstuff]]s, such as [[starch]]es ([[polysaccharide]]s), and to lower levels with usage by [[catabolism]], particularly after [[stress (medicine)|stress]], [[temperature regulation]] and [[exercise|physical exertion]]. Another input to glycemia levels is [[gluconeogenesis]], whereby [[glycogen]] stored in the [[liver]] and [[skeletal muscle]]s, or [[amino acid]]s and [[lipid]]s are converted to glucose via several metabolic chains. Excess glucose is converted to glycogen or to [[triglyceride]]s for energy storage.
Glucose is the most important source of metabolic energy for the majority of [[cell (biology)|cells]], particularly for some cells (e.g., [[neuron]]s and [[erythrocyte]]s) 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 [[convulsion]]s.
Several [[hormones]] are involved in the regulation of glucose metabolism, such as [[insulin]], [[glucagon]] (secreted by the [[pancreas]]), [[epinephrine]] (adrenaline secreted by the [[adrenal gland]]s), [[glucocorticoids]] and [[steroid hormones]] (secreted by the [[gonads]] and 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 or endovenous injection).
In certain conditions, it is recommended that [[blood glucose monitoring]] be performed regularly, usually by the patient himself, who is trained to do a digital [[venipuncture]] and use a small portable [[glucometer]] device 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 [[diabetes]] medication. Excessively high levels (e.g., 250 mg/dl or more) are classed as [[hyperglycemia]] and are a particular threat to [[diabetes]] sufferers.
* 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 [[Physical trauma|trauma]], [[stroke]], [[myocardial infarction|heart attack]], and [[surgery]] can temporarily increase glucose levels. Glycemia can also be increased by certain [[Medication|drugs]] such as [[antidepressants]], [[corticosteroids]], [[diuretics]], [[estrogen]]s, [[lithium]], [[phenothiazine]], [[phenytoin]] and [[Salicylic acid]]s, or decreased by others, such as [[acetaminophen]], [[alcohol]], [[steroids]], [[clofibrate]], [[gemfibrozil]].
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 [[cell membrane|membranes]] ([[insulin resistance]]).
==See also==
*[[Hypoglycemia]]
*[[Hyperglycemia]]
*[[Glucose]]
*[[Diabetes]]
*[[Glycemic index]]
*[[Glycemic load]]
==External links==
* [http://www.nlm.nih.gov/medlineplus/ency/article/003482.htm Glucose test]. Medline Plus.
* [http://www.nlm.nih.gov/medlineplus/ency/article/003438.htm Blood glucose monitoring]. Medline Plus.
* [http://www.nlm.nih.gov/medlineplus/ency/article/003466.htm Glucose tolerance test]. Medline Plus.
[[Category:Blood tests]]
[[Category:Physiology]]
[[es:Glucemia]]
[[it:Glicemia]]
[[pt:Glicemia]]