Ketone bodies (beta-hydroxybutyric acid & acetic acid) are used to diagnose ketonemia and ketoacidosis, which may be due to causes such as diabetes mellitus, alcoholism, stress, prolonged fasting, metabolic disorders, gastrointestinal and childhood acidemias.
Ketone body measurements can also be used in the diagnosis of isopropanol poisoning.
Ketone bodies consist of beta-hydroxybutyric (or 3-hydroxybutyric acid) and acetoacetic acid (as well as acetone to which acetoacetic acid is automatically converted). Beta-hydroxybutyric and acetoacetic acid are synthesized in the mitochondria of liver cells as a result of lipolysis and by ketogenic amino acids (leucine). The ratio of the concentrations of the two ketone bodies depends on the NAD / NADH system. High concentrations of NADH in the liver promote the formation of beta-hydroxybutyric acid (this occurs in hypoxia, fasting, and diabetic or alcoholic ketoacidosis).
Ketone bodies are alternative sources of energy (instead of glucose) for the brain, nervous system, and muscles during fasting or vigorous physical activity. The total concentration of ketone bodies in the serum is the result of a balance between liver ketogenesis and their regional consumption. Usually in normal conditions, this concentration is very low. Increased concentrations of ketone bodies are harmful and may lead to metabolic acidosis (ketoacidosis).
Physiological fluctuations in ketone bodies
The concentration of ketone bodies in serum depends on age and fasting status (concentrations of ketone bodies in the blood increase 6-fold and the ratio of beta-hydroxybutyric / acetoacetic acid increases over 2.5-3.5 times during a 15-hour fast). Increased ketonemia occurs in the following cases: prolonged fasting, vigorous physical activity, high fat diet, nutritional deficiencies during pregnancy and neonatal age, recurrent vomiting, and fever in young children.
Hyperketonemia in a normally fed patient is pathological. Concentrations of ketone bodies are increased in the following cases: uncompensated type I diabetes, alcoholic poisoning, salicylate poisoning, growth hormone deficiency, corticosteroid deficiency, and in some metabolic diseases (acetoacetyl-CoA thiolase deficiency, succinyl-CoA transferase deficiency, and pyruvate carboxylase deficiency).
In type I diabetes, monitoring of ketone bodies, especially in situations at risk of deregulation (stress, pregnancy, infections, etc.), is recommended prior to initiating insulin therapy. Elevated concentrations of ketone bodies in a diabetic patient or in a patient with persistent hyperglycemia indicate diabetic ketoacidosis, a medical emergency. In this case, the concentrations of beta-hydroxybutyrate increase.
Hyperketonemia in metabolic diseases
Hyperketonemia in combination with hypoglycemia is always pathological and may be due to hyperinsulinism or fatty acid enzyme disorders.
The increased ratio of beta-hydroxybutyric / acetoacetic acid may indicate defective mitochondrial oxidation.
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.
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