Xanthine Oxidase
Xanthine Oxidase Overview Xanthine oxidase is an enzyme that catalyzes the oxidation of hypoxanthine to xanthine and xanthine to uric acid, generating reactive oxygen species as byproducts. It plays a key role in purine metabolism and contributes to oxidative stress in various tissues. Elevated levels indicate increased enzyme activity associated with hyperuricemia, inflammation, ischemia-reperfusion injury, […]
Xanthine
Xanthine Overview Xanthine is a purine base and intermediate metabolite in the degradation pathway of purines, formed from hypoxanthine by xanthine oxidase and further converted to uric acid. It serves as a marker of purine catabolism and xanthine oxidase activity, which generates reactive oxygen species during its catalytic function. Elevated xanthine levels may indicate increased […]
Yolk Sac Protein (AFP related)
Yolk Sac Protein (AFP related) Overview Yolk sac protein refers to alpha-fetoprotein (AFP), a glycoprotein produced by the fetal yolk sac, fetal liver, and gastrointestinal tract that functions as a fetal serum albumin analog and fetal serum transport protein. It crosses the placenta minimally and peaks in maternal serum around 12-16 weeks gestation before declining. […]
YY Peptide (PYY)
YY Peptide (PYY) Overview YY peptide, or peptide YY (PYY), is a 36-amino acid gut hormone released postprandially from L-cells in the distal ileum and colon. It acts as an incretin and appetite suppressant by binding Y2 receptors in the hypothalamus to reduce food intake and inhibit gastric emptying and pancreatic secretion. Low PYY levels […]
Yersinia Antibody
Yersinia Antibody Overview Yersinia antibodies are immunoglobulins produced by the host immune system in response to infection with Yersinia species, most commonly Yersinia enterocolitica and Yersinia pseudotuberculosis. They reflect prior or ongoing exposure to these enteropathogens, which can cause gastroenteritis, mesenteric lymphadenitis, and extra‑intestinal manifestations. High titers, particularly of IgA and IgG, may indicate recent […]
Y Chromosome Microdeletion Marker
Y Chromosome Microdeletion Marker Overview Y chromosome microdeletion markers refer to specific sequence-tagged sites (STS) on the azoospermia factor (AZF) regions of the long arm of the Y chromosome that are tested for deletions causing male infertility. These markers assess the presence of genes critical for spermatogenesis, particularly in the AZFa, AZFb, and AZFc regions. […]
YKL-40
YKL-40 Overview YKL-40, also known as chitinase-3-like-1 protein (CHI3L1), is a secreted glycoprotein produced by macrophages, neutrophils, and other cells during inflammation. It lacks chitinase activity but binds chitin and regulates cell proliferation, tissue remodeling, and Th2 immune responses. Elevated serum levels indicate inflammation, tissue injury, or remodeling in conditions such as asthma, COPD, liver […]
Zinc Transporter 8 Antibody
Zinc Transporter 8 Antibody Overview Zinc transporter 8 antibody (ZnT8A) is an autoantibody targeting the zinc transporter 8 protein (SLC30A8) on insulin secretory granules in pancreatic beta cells. It appears in the autoimmune destruction of beta cells during type 1 diabetes pathogenesis, typically after GAD65 and IA-2 autoantibodies. Presence of ZnT8A increases type 1 diabetes […]
Zeta Chain Associated Protein
Zeta Chain Associated Protein Overview Zeta chain associated protein (ZAP-70) is a non-receptor tyrosine kinase expressed primarily in T cells and natural killer cells that associates with the zeta chain of the T cell receptor complex. It plays a critical role in T cell signaling by phosphorylating downstream adaptor proteins following antigen recognition, leading to […]
Zonulin
Zonulin Overview Zonulin is a protein that modulates tight junctions between epithelial cells in the intestinal mucosa, regulating gut barrier permeability. It is released in response to luminal bacteria, gluten, or other triggers, temporarily opening intercellular junctions to allow antigen sampling. Elevated serum or fecal zonulin levels indicate increased intestinal permeability ("leaky gut"), associated with […]
Zinc Protoporphyrin
Zinc Protoporphyrin Overview Zinc protoporphyrin (ZPP) is a fluorescent compound formed when zinc is incorporated into protoporphyrin IX due to reduced ferrochelatase activity and iron deficiency in erythropoietic cells. It accumulates in erythrocytes as an indicator of functional iron deficiency for hemoglobin synthesis, reflecting impaired heme production in bone marrow reticulocytes. Elevated ZPP levels indicate […]
Zinc
Zinc Overview Zinc is an essential trace element required for numerous enzymatic reactions, DNA synthesis, immune function, and protein structure stabilization as a cofactor for over 300 enzymes. It plays critical roles in immune cell development, wound healing, taste perception, and antioxidant defense through superoxide dismutase activity. Low serum zinc levels indicate deficiency associated with […]
TSH
TSH Overview TSH (thyroid-stimulating hormone) measures pituitary gland secretion that regulates thyroid hormone production, assessing the hypothalamic-pituitary-thyroid axis feedback loop. It stimulates thyroid follicular cells to produce thyroxine (T4) and triiodothyronine (T3), maintaining metabolic rate, growth, and thermogenesis. High TSH indicates primary hypothyroidism, while low TSH suggests hyperthyroidism or central hypothyroidism; it serves as the […]
Testosterone
Testosterone Overview Testosterone measures the primary male sex hormone produced mainly by testicular Leydig cells in men and ovarian theca cells in women, circulating as free hormone or bound to SHBG and albumin. It regulates masculinization, spermatogenesis, muscle mass, bone density, libido, and erythropoiesis through androgen receptor activation. Low levels indicate hypogonadism, aging, chronic illness, […]
UCP-1 Protein
UCP-1 Protein Overview UCP-1 (uncoupling protein 1) measures expression levels of this mitochondrial inner membrane protein found primarily in brown adipose tissue. It uncouples oxidative phosphorylation from ATP synthesis, dissipating proton gradient as heat through non-shivering thermogenesis activated by norepinephrine. Evidence for routine blood/plasma measurement as biomarker is limited; tissue biopsy or PET imaging preferred […]
Urate
Urate Overview Urate measures serum levels of uric acid, the final breakdown product of purine nucleotide metabolism excreted primarily by the kidneys. It serves as a major antioxidant in plasma but precipitates as monosodium urate crystals in supersaturated conditions, triggering gouty inflammation. Elevated levels indicate hyperuricemia, gout, tumor lysis syndrome, or renal impairment, while low […]
Urobilinogen
Urobilinogen Overview Urobilinogen measures colorless tetrapyrrole compound formed in the distal gut by bacterial reduction of bilirubin and partially reabsorbed into portal circulation for hepatic re-excretion. It serves as a marker of hepatic bilirubin metabolism and enterohepatic circulation integrity. Elevated urinary levels indicate hepatic dysfunction, hemolytic disorders, or biliary obstruction, while absent levels suggest complete […]
Urea
Urea Overview Urea measures serum concentration of this major nitrogenous waste product formed in the liver via the urea cycle from ammonia detoxification. It reflects hepatic synthetic function and renal clearance as the primary urinary nitrogen excretant. Elevated levels (azotemia) indicate renal impairment, dehydration, gastrointestinal bleeding, or high protein catabolism, while low levels suggest liver […]
Uric Acid
Uric Acid Overview Uric acid measures serum concentration of the final enzymatic product of purine metabolism, primarily excreted by kidneys. It functions as an antioxidant at physiological levels but forms crystals causing gout at supersaturation. Elevated levels indicate gout, tumor lysis syndrome, renal failure, or Lesch-Nyhan syndrome, while low levels rarely cause symptoms but occur […]
Vanillylmandelic Acid
Vanillylmandelic Acid Overview Vanillylmandelic acid (VMA) measures the primary urinary metabolite of catecholamines (epinephrine, norepinephrine) and their metabolites, reflecting adrenal medullary and neural crest tumor activity. It serves as a biochemical marker of catecholamine production from tyrosine via chromaffin cell tumors. Elevated levels indicate pheochromocytoma, neuroblastoma, or ganglioneuroma, while normal levels effectively exclude these diagnoses; […]