Vitamin B7 measurement is used to check hypovitaminosis and to monitor supplement therapy.
Vitamin B7 or Vitamin H is a water-soluble vitamin B complex also called biotin. Biotin acts as a cofactor in five cellular enzymes that catalyze specific carboxylation reactions. These are enzymes:
- Carboxylase of acetyl-CoA I and II: catalyze the carboxylation of acetyl-CoA to form malonyl-CoA, which in turn serves as a substrate for the elongation of fatty acids. These enzymes function in the synthesis of fatty acids and in regulating the oxidation of fatty acids in mitochondria.
- Pyruvate carboxylase: catalyzes the carboxylation of pyruvate to form oxalacetic acid, which is an intermediate in the citric acid cycle. This reaction is involved in gluconeogenesis, ie, the production of glucose from other carbohydrates from the liver, kidneys, and other tissues.
- Methylcrotonyl-CoA carboxylase: catalyzes an important step in the catabolism of leucine, an essential, branched amino acid.
- Propionyl-CoA carboxylase: catalyzes the essential steps in the metabolism of several amino acids, cholesterol, and fatty acids.
Biotin also binds to the histones, which are proteins necessary for the folding of DNA into chromatin. Thus, biotin can play a role in cell proliferation, regulation of gene expression, and cellular response to DNA damage.
Clinically apparent vitamin B7 deficiency is rare. However, significant biotin deficiency can occur in people who consume raw egg whites for extended periods. Avidin, a protein found in egg white, binds biotin and prevents its absorption. Cooking of whites destroys avidin and removes its ability to bind to biotin. Significant biotin deficiency can also occur in cases of reduced vitamin D absorption such as in patients receiving total parenteral nutrition without biotin and in some malabsorption conditions. In certain pathological conditions of the liver, the body's need for vitamin B7 may be increased and may lead to deficiency. Patients taking long-acting various anticonvulsants may also have an increased need for biotin, and it appears that biotin deficiency may be relatively common during pregnancy.
Clinical findings related to biotin deficiency include reddish rash around the eyes, nose, mouth, and genital area, and brittle nails that can coexist. Adults with biotin deficiency have hair loss and often graying of hair. Neurological symptoms of biotin deficiency include depression, lethargy, hallucinations, and limb paresthesia. Patients with hereditary disorders of biotin metabolism show impaired immune function and susceptibility to bacterial and fungal infections.
Important Note
Laboratory test results are the most important parameter for the diagnosis and monitoring of all pathological conditions. 70%-80% of diagnostic decisions are based on laboratory tests. The correct interpretation of laboratory results allows a doctor to distinguish "healthy" from "diseased".
Laboratory test results should not be interpreted from the numerical result of a single analysis. Test results should be interpreted in relation to each individual case and family history, clinical findings, and the results of other laboratory tests and information. Your personal physician should explain the importance of your test results.
At Diagnostiki Athinon we answer any questions you may have about the test you perform in our laboratory and we contact your doctor to get the best possible medical care.
