J‑Chain Protein
J‑Chain Protein Overview J‑chain protein measures a small polypeptide that is synthesized by mucosal and systemic plasma cells and becomes part of polymeric immunoglobulins, primarily secretory IgA and pentameric IgM. It facilitates the assembly of these antibodies into their multimeric forms and serves as a transport signal for polymeric IgA and IgM to bind the […]
JC Virus Antibody
JC Virus Antibody Overview JC virus antibody measures the presence and level of IgG antibodies against JC virus (JCV), a human polyomavirus that is carried latently in the kidney, central nervous system, and lymphoid tissue in many adults. JCV is the causal agent of progressive multifocal leukoencephalopathy (PML), a rare but often fatal demyelinating disease […]
JNK Protein
JNK Protein Overview JNK protein refers to c‑Jun N‑terminal kinase, a family of serine‑threonine kinases (JNK1, JNK2, JNK3) that are activated in response to cellular stress, inflammatory cytokines, and various growth factors. JNKs phosphorylate transcription factors such as c‑Jun and ATF2, regulating apoptosis, proliferation, differentiation, and inflammatory responses depending on cell context and stimulus. Because […]
JAK2 Mutation Marker
JAK2 Mutation Marker Overview JAK2 mutation marker refers to a somatic mutation in the JAK2 gene, most commonly the JAK2 V617F variant, that abnormally activates the JAK‑STAT signaling pathway and drives uncontrolled myeloid proliferation. This mutation is found in the majority of polycythemia vera and in a substantial proportion of essential thrombocythemia and primary myelofibrosis. […]
Kallikrein
Kallikrein Overview Kallikrein measures a family of serine proteases, including plasma kallikrein (KLKB1 gene) and tissue kallikreins (KLK1-15 genes), that cleave kininogens to generate vasoactive kinins or activate other protease cascades. Plasma kallikrein contributes to the contact activation pathway of coagulation and bradykinin production, while prostate-specific kallikrein-3 (PSA) is a well-established tumor marker, and other […]
Krebs Cycle Metabolites
Krebs Cycle Metabolites Overview Krebs cycle metabolites measure the concentrations of tricarboxylic acid (TCA) cycle intermediates such as citrate, alpha-ketoglutarate, succinate, fumarate, and malate in biological samples. These compounds are central to cellular respiration, linking carbohydrate, fat, and protein metabolism to the electron transport chain while also serving as precursors for amino acid, nucleotide, and […]
Kappa Free Light Chains
Kappa Free Light Chains Overview Kappa free light chains (κFLC) measure the concentration of unbound immunoglobulin kappa light chains in serum that are not paired with heavy chains to form intact antibodies. These light chains are produced by plasma cells and B‑cells and are normally present at low levels; an excess reflects abnormal plasma‑cell activity […]
Ketones
Ketones Overview Ketones measure the concentration of ketone bodies (acetoacetate, beta‑hydroxybutyrate, and acetone) in blood or urine, which are produced by the liver during fatty‑acid oxidation when glucose availability is low or insulin action is impaired. They serve as alternative energy substrates for the brain, heart, and skeletal muscle during fasting, prolonged exercise, or carbohydrate‑restricted […]
Potassium (K)
Potassium (K) Overview Potassium (K) measures the concentration of this essential intracellular cation in blood, primarily in the extracellular fluid, where it is tightly regulated by the kidneys and influenced by acid–base balance and hormonal activity. Potassium is critical for maintaining the resting membrane potential of excitable cells, including cardiac myocytes, skeletal muscle, and neurons, […]
Leptin
Leptin Overview Leptin measures a hormone primarily secreted by adipose tissue that circulates bound to proteins and signals the hypothalamus to regulate energy balance and appetite. It inhibits hunger and promotes energy expenditure; resistance to leptin signaling is common in obesity despite high circulating levels. Elevated leptin indicates obesity or leptin resistance; low levels suggest […]
LH (Luteinizing Hormone)
LH (Luteinizing Hormone) Overview Luteinizing hormone (LH) measures a glycoprotein hormone secreted by gonadotroph cells in the anterior pituitary gland under GnRH stimulation. LH stimulates ovulation and corpus luteum formation in females, and testosterone production by Leydig cells in males. Elevated levels indicate primary gonadal failure, menopause, or PCOS; low levels suggest secondary hypogonadism or […]
Lactate
Lactate Overview Lactate measures the concentration of lactic acid (lactate anion) in blood, the end product of anaerobic glycolysis when oxygen demand exceeds supply. It serves as a marker of tissue perfusion, metabolic stress, and oxygen debt during critical illness. Elevated levels indicate conditions like sepsis, shock, heart failure, or severe exercise, while very low […]
Direct Bilirubin
Direct Bilirubin Overview Direct bilirubin measures the conjugated fraction of bilirubin in serum, representing the portion processed by the liver and water-soluble for biliary excretion. It reflects hepatic conjugation efficiency and biliary patency. Elevated levels indicate cholestasis, hepatocellular dysfunction, Dubin-Johnson syndrome, or Rotor syndrome, while low levels lack clinical significance. Clinically, direct bilirubin distinguishes obstructive […]
D-Dimer
D-Dimer Overview D-dimer is a degradation product of cross-linked fibrin, and its measurementreflects ongoing activation of the coagulation and fibrinolytic systems. Itbecomes elevated when fibrin clots are formed and subsequently broken down,such as in venous thromboembolism (VTE) or disseminated intravascularcoagulation (DIC). High levels are nonspecific but may indicate thrombosis,DIC, recent surgery, trauma, infection, or malignancy, […]
DHEA-S
DHEA-S Overview Dehydroepiandrosterone sulfate (DHEA‑S) is a sulfated adrenal androgen measured in blood that reflects adrenal androgen production. It is produced mainly by the adrenal cortex and serves as a precursor for more potent androgens and estrogens in peripheral tissues. Elevated levels may indicate androgen‑secreting adrenal tumors, polycystic ovary syndrome (PCOS), or congenital adrenal hyperplasia, […]
Erythropoietin
Erythropoietin Overview Erythropoietin (EPO) is a glycoprotein hormone primarily produced by peritubular fibroblasts in the kidney that stimulates red blood cell production (erythropoiesis) in bone marrow by binding to EPO receptors on erythroid progenitor cells. It responds to hypoxia via hypoxia-inducible factor (HIF) pathway activation. Elevated levels occur in hypoxia, high-altitude exposure, inappropriate EPO secretion […]
Epinephrine
Epinephrine Overview Epinephrine measures the catecholamine hormone and neurotransmitter secreted primarily by the adrenal medulla in response to stress, serving critical roles in the fight-or-flight response through stimulation of alpha and beta adrenergic receptors. It increases heart rate, cardiac output, bronchodilation, and blood glucose while redirecting circulation to vital organs. Elevated levels indicate pheochromocytoma, paraganglioma, […]
Eosinophils
Eosinophils Overview Eosinophils measure the absolute count or percentage of a type of white blood cell involved in allergic responses, parasitic infections, and immune regulation. These granulocytes release cytotoxic granules containing major basic protein, eosinophil cationic protein, and other mediators that target parasites and modulate inflammation. Elevated levels (eosinophilia) indicate allergic disorders, parasitic infections, drug […]
ESR (Erythrocyte Sedimentation Rate)
ESR (Erythrocyte Sedimentation Rate) Overview ESR measures the rate at which erythrocytes settle in anticoagulated blood over one hour, serving as a nonspecific indicator of inflammation through increased plasma proteins like fibrinogen and globulins that cause red blood cell rouleaux formation. It reflects the acute phase response but lacks organ specificity. Elevated ESR indicates inflammatory […]
Estradiol
Estradiol Overview Estradiol (E2) is the primary biologically active estrogen in premenopausal women, produced mainly by the ovaries, with smaller contributions from adrenal glands and peripheral conversion of androgens. It plays key roles in development of secondary sexual characteristics, regulation of the menstrual cycle, bone metabolism, and cardiovascular and neurological function. High levels may be […]