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The liver produces urea in the urea cycle as a waste product of the digestion of protein. Normal human adult blood should contain between 6 to 20 mg of urea nitrogen per 100 ml (6–20 mg/dL) of blood. Individual laboratories will have different reference ranges as the assay used will vary between laboratories.〔Last page of 〕〔(Normal Lab Results ) from Marshal University School of Medicine〕 ==Interpretation== Blood urea nitrogen (BUN) is an indication of renal (kidney) health. The normal range is 1.8-7.1 mmol/L or 6–20 mg/dL. The main causes of an increase in BUN are: high protein diet, decrease in glomerular filtration rate (GFR) (suggestive of renal failure) and in blood volume (hypovolemia), congestive heart failure, gastrointestinal hemorrhage,〔Longo et al., Harrison's Principles of Internal Medicine, 18th ed., p.611〕 fever and increased catabolism. Hypothyroidism can cause both decreased GFR and hypovolemia, however BUN-to-creatinine ratio has been found to be lowered in hypothyroidism and raised in hyperthyroidism. The main causes of a decrease in BUN are severe liver disease, anabolic state, and syndrome of inappropriate antidiuretic hormone.〔 Another cause of a decreased BUN is ornithine transcarbamylase deficiency, which is a genetic disorder inherited in an X-linked recessive pattern. OTC Deficiency is also accompanied by hyperammonemia and high orotic acid levels. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「blood urea nitrogen」の詳細全文を読む スポンサード リンク
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