Free T4
Free T4 Overview Free T4 measures the unbound, biologically active fraction of thyroxine (T4), the major hormone secreted by the thyroid gland that regulates metabolism, growth, and development through nuclear receptor binding. It represents the physiologically available thyroid hormone not bound to carrier proteins (thyroid-binding globulin, albumin, transthyretin). Elevated levels indicate hyperthyroidism (Graves disease, toxic […]
Fibrinogen
Fibrinogen Overview Fibrinogen measures a soluble plasma glycoprotein synthesized by the liver that serves as the precursor to fibrin during blood clotting. As an acute phase reactant, it rises rapidly in response to inflammation, tissue injury, or infection. Elevated levels indicate inflammation, pregnancy, or thrombotic risk, while low levels suggest bleeding disorders, liver disease, or […]
Folate
Folate Overview Folate measures the concentration of this essential B vitamin (vitamin B9) in blood, primarily as a cofactor in one-carbon metabolism for DNA synthesis, methylation reactions, and amino acid metabolism. Serum folate reflects recent dietary intake, while red blood cell folate indicates long-term tissue stores. Low levels indicate dietary deficiency, malabsorption, increased demand (pregnancy), […]
Ferritin
Ferritin Overview Ferritin measures the intracellular iron storage protein that reflects total body iron stores in healthy individuals. It sequesters iron to prevent free radical formation and releases it as needed for hemoglobin synthesis and other metabolic functions. Elevated levels indicate iron overload, inflammation, liver disease, or malignancy, while low levels signal iron deficiency anemia. […]
Glutathione
Glutathione Overview Glutathione is a tripeptide antioxidant synthesized intracellularly that maintains cellular redox balance, detoxifies xenobiotics, and regenerates vitamins C and E. As the most abundant non-protein thiol, it exists in reduced (GSH) and oxidized (GSSG) forms, with the GSH:GSSG ratio reflecting oxidative stress status. Low levels indicate oxidative stress, chronic inflammation, liver disease, or […]
Growth Hormone
Growth Hormone Overview Growth hormone (GH) measures a peptide hormone secreted by the anterior pituitary gland in pulsatile fashion that stimulates insulin-like growth factor-1 (IGF-1) production in liver and promotes linear growth, protein synthesis, and lipolysis. It binds membrane receptors to activate JAK-STAT signaling. Elevated levels indicate acromegaly or gigantism from pituitary adenoma, while low […]
Globulin
Globulin Overview Globulin measures the major class of serum proteins excluding albumin, comprising immunoglobulins, transport proteins (transferrin, haptoglobin), complement proteins, and acute phase reactants. Total globulin (total protein minus albumin) reflects immune function, liver synthetic capacity, and inflammatory status. Elevated levels indicate polyclonal gammopathy (chronic inflammation, infection, autoimmune disease), monoclonal gammopathy (multiple myeloma), or dehydration, […]
Gamma-Glutamyl Transferase (GGT)
Gamma-Glutamyl Transferase (GGT) Overview Gamma-glutamyl transferase (GGT) measures an enzyme predominantly located on the canalicular membrane of hepatocytes and biliary epithelial cells that catalyzes the transfer of gamma-glutamyl groups from glutathione to acceptors. It plays a role in amino acid transport and detoxification of xenobiotics. Elevated levels primarily indicate hepatobiliary disease (cholestasis, alcohol-related liver injury) […]
Glucose (Fasting)
Glucose (Fasting) Overview Fasting glucose measures blood glucose concentration after an overnight fast, serving as the primary indicator of carbohydrate metabolism and pancreatic beta-cell insulin secretory function. Glucose is the main energy source for cells, with levels tightly regulated by insulin and counter-regulatory hormones. Elevated levels indicate prediabetes, diabetes mellitus, or acute stress hyperglycemia, while […]
Haptoglobin
Haptoglobin Overview Haptoglobin is a glycoprotein produced by the liver that binds free hemoglobin released during intravascular hemolysis, forming a haptoglobin–hemoglobin complex that is cleared by the reticuloendothelial system. This protects the kidneys from hemoglobin‑induced oxidative damage and prevents iron loss through urine. Low levels usually indicate ongoing intravascular hemolysis, liver disease, or chronic inflammation, […]
Homocysteine
Homocysteine Overview Homocysteine measures the sulfur-containing amino acid formed during the metabolism of methionine, which is then recycled to methionine by vitamin B12‑dependent methionine synthase or converted to cysteine by vitamin B6‑dependent enzymes. Chronically elevated levels (hyperhomocysteinemia) reflect impaired one‑carbon metabolism, often due to B‑vitamin deficiency (folate, B12, B6), genetic variants (e.g., MTHFR), or renal […]
HDL Cholesterol
HDL Cholesterol Overview HDL cholesterol measures the cholesterol content carried by high-density lipoprotein particles, which are involved in reverse cholesterol transport from peripheral tissues back to the liver for excretion. HDL particles also have anti-inflammatory, antioxidant, and antithrombotic functions that may protect against atherosclerosis. Low HDL levels are associated with increased cardiovascular risk, while higher […]
7-Dehydrocholesterol
7-Dehydrocholesterol Overview 7-Dehydrocholesterol is a sterol precursor in the cholesterol biosynthesis pathway and the immediate precursor to vitamin D3 in skin upon ultraviolet B exposure. It accumulates in Smith-Lemli-Opitz syndrome (SLOS) due to 7-dehydrocholesterol reductase (DHCR7) deficiency, impairing cholesterol synthesis and causing characteristic developmental abnormalities. Elevated plasma levels indicate SLOS, while normal levels help exclude […]
5-HIAA
5-HIAA Overview 5-Hydroxyindoleacetic acid (5-HIAA) is the primary urinary metabolite of serotonin, formed by monoamine oxidase and aldehyde dehydrogenase metabolism in the liver, kidney, and brain. It reflects systemic serotonin production and turnover, primarily from enterochromaffin cells in the gut but pathologically elevated in serotonin-producing neuroendocrine tumors. High urinary 5-HIAA levels indicate carcinoid syndrome or […]
17-Hydroxyprogesterone
17-Hydroxyprogesterone Overview 17-Hydroxyprogesterone is a steroid intermediate in the production of cortisol and androgens by the adrenal cortex and gonads. It serves as a marker of adrenal steroidogenesis, particularly 21-hydroxylase activity in the cortisol synthesis pathway. Elevated levels indicate congenital adrenal hyperplasia (most commonly 21-hydroxylase deficiency), while low levels suggest adrenal insufficiency or 17-alpha-hydroxylase deficiency. […]
1,25-Dihydroxyvitamin D
1,25-Dihydroxyvitamin D Overview 1,25-Dihydroxyvitamin D [1,25(OH)2D], also known as calcitriol, is the active hormonal form of vitamin D produced by 1-alpha-hydroxylation of 25-hydroxyvitamin D in the kidney. It regulates calcium and phosphate homeostasis by promoting intestinal absorption, bone resorption, and renal reabsorption while suppressing parathyroid hormone secretion. Low levels indicate renal failure, hypoparathyroidism, or 1-alpha-hydroxylase […]
25-Hydroxyvitamin D
25-Hydroxyvitamin D Overview 25-Hydroxyvitamin D [25(OH)D] is the major circulating form of vitamin D and serves as the best indicator of vitamin D nutritional status and metabolic function. It is formed in the liver by hydroxylation of vitamin D2 or D3 and reflects contributions from sunlight exposure, diet, and supplements before conversion to active 1,25-dihydroxyvitamin […]
Alkaline Phosphatase
Alkaline Phosphatase Overview Alkaline phosphatase (ALP) is an enzyme found in various tissues, primarily liver, bone, intestine, and placenta, that catalyzes the hydrolysis of phosphate esters at alkaline pH. It plays a key role in bone mineralization and liver bile processing. Elevated levels may indicate liver disease (e.g., cholestasis, hepatitis), bone disorders (e.g., Paget’s disease, […]
Albumin
Albumin Overview Albumin is the most abundant protein in blood plasma, primarily produced by the liver, and it measures nutritional status, liver synthetic function, and vascular permeability. It maintains oncotic pressure to prevent fluid leakage from blood vessels and transports hormones, drugs, and fatty acids. Low levels (hypoalbuminemia) often indicate chronic liver disease, malnutrition, kidney […]
Aldosterone
Aldosterone Overview Aldosterone is a steroid hormone produced by the adrenal cortex that primarilyregulates sodium and potassium balance in the body by promoting sodiumreabsorption and potassium excretion in the kidneys. Elevated levels mayindicate primary aldosteronism, such as adrenal adenoma or hyperplasia, whilelow levels can occur in adrenal insufficiency. It is clinically useful fordiagnosing hypertension causes, […]