human physiology The human body is the entire structure of a human being. It is composed of many different types of cells that together create tissues and subsequently organs and then organ systems. The external human body consists of a head, hair, neck, ...

, nitrogen balance is the net difference between bodily nitrogen intake (ingestion) and loss (excretion). It can be represented as the following:

\mbox =  -

Nitrogen is a fundamental chemical component of

amino acids Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although over 500 amino acids exist in nature, by far the most important are the Proteinogenic amino acid, 22 α-amino acids incorporated into p ...

, the molecular building blocks of

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

. As such, nitrogen balance may be used as an index of

protein metabolism Protein metabolism denotes the various biochemical processes responsible for the synthesis of proteins and amino acids (anabolism), and the breakdown of proteins by catabolism. The steps of protein synthesis include transcription, translation, an ...

. When more nitrogen is gained than lost by an individual, they are considered to have a positive nitrogen balance and be in a state of overall protein anabolism. In contrast, a negative nitrogen balance, in which more nitrogen is lost than gained, indicates a state of overall protein

catabolism Catabolism () is the set of metabolic pathways that breaks down molecules into smaller units that are either oxidized to release energy or used in other anabolic reactions. Catabolism breaks down large molecules (such as polysaccharides, lipid ...

. The body obtains nitrogen from dietary

, sources of which include meat, fish, eggs, dairy products, nuts, legumes, cereals, and grains. Nitrogen loss occurs largely through urine in the form of

urea Urea, also called carbamide (because it is a diamide of carbonic acid), is an organic compound with chemical formula . This amide has two Amine, amino groups (–) joined by a carbonyl functional group (–C(=O)–). It is thus the simplest am ...

, as well as through faeces, sweat, and growth of hair and skin. Blood urea nitrogen and urine urea nitrogen tests can be used to estimate nitrogen balance.

Physiological and Clinical Implications

Positive nitrogen balance is associated with periods of growth,

hypothyroidism Hypothyroidism is an endocrine disease in which the thyroid gland does not produce enough thyroid hormones. It can cause a number of symptoms, such as cold intolerance, poor ability to tolerate cold, fatigue, extreme fatigue, muscle aches, co ...

, tissue repair, and pregnancy. Negative nitrogen balance is associated with burns, serious tissue injuries, fever,

hyperthyroidism Hyperthyroidism is a endocrine disease in which the thyroid gland produces excessive amounts of thyroid hormones. Thyrotoxicosis is a condition that occurs due to elevated levels of thyroid hormones of any cause and therefore includes hyperth ...

, wasting diseases, and periods of fasting. A negative nitrogen balance can be used as part of a clinical evaluation of malnutrition. Nitrogen balance is a method traditionally used to measure dietary protein requirements. This approach necessitates the meticulous collection of all nitrogen inputs and outputs to ensure comprehensive accounting of nitrogen exchanges. Nitrogen balance studies typically involve controlled dietary conditions, requiring participants to consume specific diets to determine total nitrogen intake precisely. Furthermore, participants often must remain at the study location for the duration of the study to facilitate the collection of all nitrogen losses. Physical exercise is also known to influence nitrogen excretion, adding another variable that requires control during these studies. Due to the stringent conditions required for accurate results, the nitrogen balance method may pose challenges when studying dietary protein requirements across different demographics, such as children.

References

External links

* {{cite web, title=Test Definition: NITF, website=Mayo Clinic Laboratories, url=https://www.mayocliniclabs.com/api/sitecore/TestCatalog/DownloadTestCatalog?testId=607704 (with clinical information & interpretation related to nitrogen balance and its clinical testing) Nitrogen Proteins

Physiological and Clinical Implications

See also

References

External links