Table of Contents


achlorhydria: absence of hydrochloric acid from the gastric juice

acidosis: a pathologic state characterized by an increase in the concentration of hydrogen ions in the arterial blood above normal level, 40 nmol/L, or pH 7.4

acute coronary syndrome (ACS): a wide range of acute heart conditions including ST-segment elevation myocardial infarction, non-ST-segment myocardial infarction and unstable angina

acute myocardial infarction (AMI), also myocardial infarction (MI): infarction of a segment of the heart muscle, usually as a result of occlusion of a coronary artery

acute pancreatitis: an acute inflammation of the pancreas accompanied by the formation of necrotic areas and hemorrhage into the substance of the gland; clinically marked by sudden severe abdominal pain, nausea, fever, and leukocytosis; areas of fat necrosis are present on the surface of the pancreas and in the omentum because of the action of the escaped pancreatic enzyme (trypsin and lipase)

adenoma: a benign epithelial neoplasm in which the tumor cells form glands or gland-like structures; usually well circumscribed, tending to compress rather than infiltrate or invade adjacent tissue

adrenocorticotrophic hormone (ACTH): a 39 amino-acid peptide hormone secreted by anterior pituitary that acts primarily on the adrenal cortex stimulating its growth and its secretion of corticosteroids

alanine aminotransferase (ALT): an enzyme transferring amino groups from l-alanine to 2-ketoglutarate, or the reverse (from l-glutamate to pyruvate); there is a d-alanine transaminase that effects the same reaction, but using d-alanine and d-glutamate; serum concentration is increased in viral hepatitis and myocardial infarction

alkaline phosphatase: a phosphatase with an optimum pH of above 7.0 (e.g., 8.6), present ubiquitously; localized cytochemically in membranes by modifications of Gomori nonspecific alkaline phosphatase stain; it hydrolyzes many orthophosphoric monoesters; low levels of this enzyme are seen in cases of hypophosphatasia

alkalosis: a state characterized by a decrease in the hydrogen ion concentration of arterial blood below normal level, 40 nmol/L, or Ph 7.4; the condition may be caused by an increase in the concentration of alkaline compounds, or by a decrease in the concentration of acidic compounds or carbon dioxide

amylase: one of a group of amylolytic enzymes that cleave starch, glycogen, and related 1,4-α-glucans

anemia: any condition in which the number of red blood cells per mm3, the amount of hemoglobin in 100 ml of blood, and/or the volume of packed red blood cells per 100 ml of blood are less than normal; clinically, generally pertaining to the concentration of oxygen-transporting material in a designated volume of blood; anemia is frequently manifested by pallor of the skin and mucous membranes, shortness of breath, palpitations of the heart, soft systolic murmurs, lethargy, and fatigability

anion gap: the difference between the sum of the measured cations and anions in the plasma or serum calculated as follows: (Na+ + K+) - (Cl- + HCO3-); elevated values may occur in diabetic or lactic acidosis; normal or low values occur in bicarbonate-losing metabolic acidoses

anuria: absence of urine formation

aplastic anemia: anemia characterized by a greatly decreased formation of erythrocytes and hemoglobin, usually associated with pronounced granulocytopenia and thrombocytopenia, as a result of hypoplastic or aplastic bone marrow

apolipoproteins: the protein component of any lipoprotein complexes

apotransferrin: plasma iron binding protein with no iron bound

aspartate aminotransferase (AST): an enzyme catalyzing the reversible transfer of an amine group from l-glutamic acid to oxaloacetic acid, forming α-ketoglutaric acid and l-aspartic acid; a diagnostic aid in viral hepatitis

azotemia: an abnormal increase in concentration of urea and other nitrogenous substances in the blood plasma


B cell lymphocyte: an immunologically important lymphocyte that is not thymus-dependent, is of short life, and resembles the bursa-derived lymphocyte of birds in that it is responsible for the production of immunoglobulins, i.e. it is the precursor of the plasma cell and expresses immunoglobulins on its surface but does not release them; it does not play a direct role in cell-mediated immunity

basophil: a cell with granules that stain specifically with basic dyes; a phagocytic leukocyte of the blood characterized by numerous basophilic granules containing heparin and histamine and leukotrienes; except for its segmented nucleus, it is morphologically and physiologically similar to the mast cell though they originate from different stem cells in the bone marrow

Bence Jones protein: proteins with unusual thermosolubility found in the urine of patients with multiple myeloma, consisting of monoclonal immunoglobulin light chains

benign: denoting the mild character of an illness or the nonmalignant character of a neoplasm

bilirubin: a yellow bile pigment found as sodium bilirubinate (soluble), or as an insoluble calcium salt in gallstones; formed from hemoglobin during normal and abnormal destruction of erythrocytes by the reticuloendothelial system; excess bilirubin is associated with jaundice


cancer: general term frequently used to indicate any of various types of malignant neoplasms, most of which invade surrounding tissues, may metastasize to several sites, and are likely to recur after attempted removal and to cause death of the patient unless adequately treated; especially, any such carcinoma or sarcoma, but, in ordinary usage, especially the former

cardiac markers: proteins used to monitor damage to cardiac tissue, typically cTnI, cTnT, CKMB, and Myoglobin

cholestasis: an arrest in the flow of bile; cholestasia due to obstruction of bile ducts is accompanied by formation of plugs of inspissated bile in the small ducts, canaliculi in the liver, and elevation of serum direct bilirubin and some enzymes

chronic pancreatitis: repeated exacerbations of pancreatitis in patient with chronic inflammation of that organ; relapses are usually due to persistence of etiologic factor or repeated exposure to it, such as occurs with partial ductal obstruction or chronic alcoholism

chylomicron: a large lipid droplet of reprocessed lipid synthesized in epithelial cells of the small intestine and containing triacylglycerols, cholesterol esters, and several apolipoproteins

cirrhosis: end stage liver disease characterized by diffuse damage to hepatic parenchymal cells, with nodular regeneration, fibrosis, and disturbance of normal architecture; associated with failure in the function of hepatic cells and interference with blood flow in the liver, frequently resulting in jaundice, portal hypertension, ascites, and ultimately biochemical and functional signs of hepatic failure

coagulation: clotting; the process of changing from a liquid to a solid, said especially of blood (i.e., blood coagulation); in vertebrates, blood coagulation is a result of cascade regulation from fibrin

coefficient of variation: the ratio of standard deviation to the mean

congenital: existing at birth, referring to certain mental or physical traits, anomalies, malformations, diseases etc. which may be either hereditary or due to an influence occurring during gestation up to the moment of birth

congenital adrenal hyperplasia: a group of autosomal recessively inherited disorders associated with a deficiency of one of the enzymes involved in cortisol biosynthesis, resulting in elevation of ACTH levels and overproduction and accumulation of cortisol precursors proximal to the block; androgens are produced in excess, causing virilization; the most common disorder is the 21-hydroxylase deficiency, caused by mutation in the cytochrome P450 21-hydroxylase gene (CYP21) on chromosome 6p; there are four major types with some clinical similarities but distinctive genetic and biochemical differences

congestive heart failure: inadequacy of the heart so that as a pump it fails to maintain the circulation of blood, with the result that congestion and edema develop in the tissues

corticosteroid: a steroid produced by the adrenal cortex (i.e., adrenal corticoid); a corticoid containing a steroid

corticotrophin releasing hormone (CRH): a factor secreted by the hypothalamus that stimulates the pituitary to release adrenocorticotropic hormone

creatinine: a component of urine and the final product of creatine catabolism; formed by the nonenzymatic dephosphorylative cyclization of phosphocreatine to form the internal anhydride of creatine

creatine kinase (CK): an enzyme catalyzing the reversible transfer of phosphate from phosphocreatine to ADP, forming creatine and ATP; of importance in muscle contraction

creatine kinase MB (CKMB): an enzyme catalyzing the reversible transfer of phosphate from phosphocreatine to ADP, forming creatine and ATP; of importance in muscle concentration; certain isozymes are elevated in plasma following myocardial infarctions

cystic fibrosis: a congenital metabolic disorder in which secretions of exocrine glands are abnormal; excessively viscid mucus causes obstruction of passageways (including pancreatic and bile ducts, intestines, and bronchi), and the sodium and chloride content of sweat are increased throughout the patient’s life; symptoms usually appear in childhood and include meconium ileus, poor growth despite good appetite, malabsorption and foul bulky stools, chronic bronchitis with cough, recurrent pneumonia, bronchiectasis, emphysema, clubbing of the fingers, and salt depletion in hot weather; detailed genetic mapping and molecular biology have been accomplished by the methods of reverse genetics; autosomal recessive inheritance, caused by mutation in the cystic fibrosis conductance regulator gene (CFTR) on chromosome 7q


diabetes mellitus: chronic metabolic disorder in which utilization of carbohydrate is impaired and that of lipid and protein enhanced; it is caused by an absolute or relative deficiency of insulin and is characterized, in more severe cases, by chronic hyperglycemia, glycosuria, water and electrolyte loss, ketoacidosis, and coma; long-term complications include neuropathy, retinopathy, nephropathy, generalized degenerative changes in large and small blood vessels, and increased susceptibility to infection

direct bilirubin: the fraction of serum bilirubin which has been conjugated with glucuronic acid in the liver cell to form bilirubin diglucuronide; so called because it reacts directly with the Ehrlich diazo reagent; increased levels are found in hepatobiliary diseases, especially of the obstructive variety

disseminated intravascular coagulation (DIC): a hemorrhagic syndrome that occurs following the uncontrolled activation of clotting factors and fibrinolytic enzymes throughout small blood vessels; fibrin is deposited, platelets and clotting factors are consumed, and fibrin degradation products inhibit fibrin polymerization, resulting in tissue necrosis and bleeding

dyslipidemia: disorder of lipoprotein metabolism

dyspnea: Shortness of breath, a subjective difficulty or distress in breathing


emergency toxicology: the laboratory diagnosis of the presence and severity of drug overdose, often in the comatose or obtunded patient

eosinophil: a polymorphonuclear leukocyte characterized by many large or prominent, refractile, cytoplasmic granules that are fairly uniform in size and bright yellow-red or orange when treated with Wright or similar stains; the nuclei are usually larger than those of neutrophils, do not stain as deeply, and characteristically have two lobes (a third lobe is sometimes interposed on the connecting strand of chromatin); these leukocytes are motile phagocytes with distinctive antiparasitic functions


ferritin: an iron-protein complex, containing up to 23% iron, formed by the union of ferric ions with apoferritin; it is found in the intestinal mucosa, spleen, bone marrow, reticulocytes, and liver, and regulates iron storage and transport from the intestinal lumen to plasma

folic acid: a collective term for pteroylglutamic acids and their oligoglutamic acid conjugates; a collective term for pteroylglutamic acids and their oligoglutamic acid conjugates; N-[p-[[(2-Amino-4-hydroxypteridin-6-yl)methyl]amino]benzoyl]-L(+)-glutamic acid; specifically, pteroylmonoglutamic acid; the growth factor for Lactobacillus casei, and a member of the vitamin B complex necessary for the normal production of red blood cells; present, with or without L(+)- glutamic acid moieties, in peptide linkages in liver, green vegetables, and yeast; used to treat folate deficiency and megaloblastic anemia


gamma glutamyl transferase (GGT): an enzyme that catalyzes the transfer of a γ-glutamyl group from a γ-glutamyl peptide to an acceptor

gastroesophageal reflux disease (GERD): a regurgitation of the contents of the stomach into the esophagus, possibly into the pharynx where they can be aspirated between the vocal cords and down into the trachea; symptoms of burning pain and acid taste result; pulmonary complications of aspiration are dependent upon the amount, content, and acidity of the aspirate

glomerular: relating to or affecting a glomerulus or the glomeruli

gluconeogenesis: the formation of glucose from noncarbohydrates, such as protein or fat

glycogenolysis: the hydrolysis of glycogen to glucose

glycosuria: urinary excretion of carbohydrates

granular leukocytes: any one of the polymorphonuclear leukocytes, especially a neutrophilic leukocyte


hematocrit (HCT): percentage of the volume of a blood sample occupied by cells
hemoglobin (HGB): the red respiratory protein of erythrocytes, consisting of approximately 3.8% heme and 96.2% globin, with a molecular weight of 64,450, which as oxyhemoglobin (HbO2) transports oxygen from the lungs to the tissues where the oxygen is readily released and HbO2 becomes Hb;

when Hb is exposed to certain chemicals, its normal respiratory function is blocked; e.g., the oxygen in HbO2 is easily displaced by carbon monoxide, thereby resulting in the formation of fairly stable carboxyhemoglobin (HbCO), as in asphyxiation resulting from inhalation of exhaust fumes from gasoline engines;

when the iron in Hb is oxidized from the ferrous to ferric state, as in poisoning with nitrates and certain other chemicals, a nonrespiratory compound, methemoglobin (MetHb), is formed;

in humans there are at least five kinds of normal Hb: two embryonic Hb’s (Hb Gower-1, Hb Gower-2), fetal (Hb F), and two adult types (Hb A, Hb A2); there are two α globin chains containing 141 amino acid residues, and two of another kind (β, γ, δ, ε, or ζ), each containing 146 amino acid residues in four of the Hb’s; Hb Gower-1 has two ζ chains and two ε chains; the production of each kind of globin chain is controlled by a structural gene of similar Greek letter designation; normal individuals are homozygous for the normal allele at each locus; substitution of one amino acid for another in the polypeptide chain can occur at any codon in any of the five loci and have resulted in the production of many hundreds of abnormal Hb types, most of no known clinical significance; in addition, deletions of one or more amino acid residues are known, as well as gene rearrangements due to unequal crossing over between homologous chromosomes;

the Hb types below are the main abnormal types known to be of clinical significance; newly discovered abnormal Hb types are first assigned a name, usually the location where discovered, and a molecular formula is added when determined; the formula consists of Greek letters to designate the basic chains, with subscript 2 if there are two identical chains; a superscript letter (A if normal for adult Hb, etc.) is added, or the superscript may designate the site of amino acid substitution (numbering amino acid residues from the N-terminus of the polypeptide) and specifying the change, using standard abbreviations for the amino acids; there is an exhaustive listing of variant hemoglobins in MIM where a composite numbering system is used

hemoglobin S disease: an abnormal Hb with substitution of valine for glutamic acid at the 6th position of the β chain; the formula is α2Aβ2S, or, more specifically, α2Aβ26Glu→Val; heterozygous state: sickle cell trait, no anemia, Hb S 20-45% of total, the rest Hb A; homozygous state: sickle cell anemia, Hb S 75-100% of total, the rest Hb F or Hb A2

hemoglobin S trait: heterozygous state in which there is one normal beta chain and one sickle beta chain, no clinical or hematological manifestations

hemostasis: the arrest of bleeding

hepatitis: inflammation of the liver, due usually to viral infection but sometimes to toxic agents

hyperaldosteronism: a disorder caused by excessive secretion of aldosterone

hyperglycemia: an abnormally high concentration of glucose in the circulating blood, seen especially in patients with diabetes mellitus

hyperthyroidism: an abnormality of the thyroid gland in which secretion of thyroid hormone is usually increased and is no longer under regulatory control of hypothalamic-pituitary centers; characterized by a hypermetabolic state, usually with weight loss, tremulousness, elevated plasma levels of thyroxin and/or triiodothyronine, and sometimes exophthalmos; may progress to severe weakness, wasting, hyperpyrexia, and other manifestations of thyroid storm; often associated with exophthalmos (Grave’s disease)

hyperthyroxinemia: an elevated thyroxine concentration in the blood

hypoplastic anemia: progressive nonregenerative anemia resulting from greatly depressed, inadequately functioning bone marrow; as the process persists, aplastic anemia may occur

hypothyroidism: diminished production of thyroid hormone, leading to clinical manifestations of thyroid insufficiency, including low metabolic rate, tendency to weight gain, somnolence and sometimes myxedema

hypothyroxinemia: a subnormal thyroxine concentration in the blood


indirect bilirubin: the fraction of serum bilirubin which has not been conjugated with glucuronic acid in the liver cell; so called because it reacts with the Ehrlich diazo reagent only when alcohol is added; increased levels are found in hepatic disease and hemolytic conditions

interindividual variation: deviation in true value of an analyte between individuals

intraindividual variation: deviation in true value of an analyte within the same individual

iron: a metallic element, atomic no. 26, atomic wt. 55.847, that occurs in the heme of hemoglobin, myoglobin, transferrin, ferritin, and iron-containing porphyrins, and is an essential component of enzymes such as catalase, peroxidase, and the various cytochromes; its salts are used medicinally

isoenzyme: one of a group of enzymes that catalyze the same reaction but may be differentiated by variations in physical properties, such as isoelectric point or modes of regulation

isosthenuria: a state in chronic renal disease in which the kidney cannot form urine with a higher or a lower specific gravity than that of protein free plasma; specific gravity of the urine becomes fixed around 1.010, irrespective of the fluid intake


ketonemia: the presence of recognizable concentrations of ketone bodies in the plasma

ketonuria: enhanced urinary excretion of ketone bodies


leukemia: progressive proliferation of abnormal leukocytes found in hemopoietic tissues, other organs, and usually in the blood in increased numbers; leukemia is classified by the dominant cell type, and by duration from onset to death; this occurs in acute leukemia within a few months in most cases, and is associated with acute symptoms including severe anemia, hemorrhages, and slight enlargement of lymph nodes or the spleen; the duration of chronic leukemia exceeds one year, with a gradual onset of symptoms of anemia or marked enlargement of spleen, liver, or lymph nodes

leukocytes: a type of cell formed in the myelopoietic, lymphoid, and reticular portions of the reticuloendothelial system in various parts of the body, and normally present in those sites and in the circulating blood (rarely in other tissues); under various abnormal conditions, the total numbers or proportions, or both, may be characteristically increased, decreased, or not altered, and they may be present in other tissues and organs;

leukocytes represent three lines of development from primitive elements: myeloid, lymphoid, and monocytic series; on the basis of features observed with various methods of staining with polychromatic dyes (e.g., Wright stain) cells of the myeloid series are frequently termed granular leukocytes, or granulocytes; cells of the lymphoid and monocytic series also have granules in the cytoplasm but, owing to their tiny, inconspicuous size and different properties (frequently not clearly visualized with routine methods), lymphocytes and monocytes are sometimes termed nongranular or agranular leukocytes; granulocytes are commonly known as polymorphonuclear leukocytes (also polynuclear or multinuclear leukocytes), inasmuch as the mature nucleus is divided into two to five rounded or ovoid lobes that are connected with thin strands or small bands of chromatin; they consist of three distinct types: neutrophils, eosinophils, and basophils, named on the basis of the staining reactions of the cytoplasmic granules

leukopenia: the antithesis of leukocytosis; any situation in which the total number of leukocytes in the circulating blood is less than normal, the lower limit of which is generally regarded as 4000-5000/mm3

lipase: in general, any fat-splitting or lipolytic enzyme; a carboxylesterase

lipid: fat soluble, an operational term describing a solubility characteristic, not a chemical substance, i.e. denoting substances extracted from animal or vegetable cells by nonpolar solvents

lipoprotein: any complex or compound containing both lipid and protein

lymphocyte: a white blood cell formed in lymphatic tissue throughout the body (e.g., lymph nodes, spleen, thymus, tonsils, Peyer patches, and sometimes in bone marrow) and in normal adults making up approximately 22-28% of the total number of leukocytes in the circulating blood; lymphocytes are divided into 2 principal groups, termed T and B cells, based on their surface molecules as well as function

lymphopenia: a reduction, relative or absolute, in the number of lymphocytes in the circulating blood


malignant: resistant to treatment; occurring in severe form, and frequently fatal; tending to become worse and leading to an ingravescent course

mean: a statistical measurement of central tendency or average of set of values

mean corpuscular hemoglobin (MCH): the hemoglobin content of the average red cell, calculated from the hemoglobin therein and the red cell count, in erythrocyte indices

MCHC: mean corpuscular hemoglobin concentration (g/dL)

MCV: mean corpuscular volume in femtoliters (fL)

metabolic acidosis: a decreased pH and bicarbonate concentration in the body fluids caused either by the accumulation of acids or by abnormal losses of fixed base from the body, as in diarrhea or renal disease

metabolic alkalosis: an alkalosis associated with an increased arterial plasma bicarbonate concentration, possibly resulting from an excessive intake of alkaline materials or an excessive loss of acid in the urine or through persistent vomiting; the base excess and standard bicarbonate are both elevated

metastasis: the shifting of a disease or its local manifestations, from one part of the body to another

monoclonal gammopathy of undetermined significance (MGUS): a paraproteinemia (an abnormal gammaglobulin, typically with λ light chain component) of less than 3 g/100 ml, which at the time of discovery, is without apparent cause; specifically, there is no evidence of multiple myeloma or other malignant disorders

monoclonal immunoglobulin: a homogeneous immunoglobulin resulting from the proliferation of a single clone of plasma cells and which, during electrophoresis of serum, appears as a narrow band or spike; it is characterized by heavy chains of a single class and subclass, and light chains of a single type

monocyte: leukocytes of the circulating blood, normally found in lymph nodes, spleen, bone marrow, and loose connective tissue

myoglobin: the oxygen-carrying and storage protein of muscle, resembling blood hemoglobin in function but containing only one subunit and one heme as part of the molecule, and with a molecular weight approximately one-quarter that of hemoglobin


negative predictive value: the fraction of negative values which are correct; determined by dividing the true negatives by the sum of the true negatives and false negatives

neutropenia: the presence of abnormally small numbers of neutrophils in the circulating blood

neutrophil: a mature white blood cell in the granulocytic series, formed by myelopoietic tissue of the bone marrow (sometimes also in extramedullary sites), and released into the circulating blood, where they normally represent 54-65% of the total number of leukocytes; the precursors of neutrophils, in order of increasing maturity, are: myeloblasts, promyelocytes, myelocytes, metamyelocytes, and band forms; although the terms neutrophilic leukocytes and neutrophilic granulocytes include younger cells in which neutrophilic granules are recognized, the two expressions are frequently used as synonyms for neutrophils, which are mature forms unless otherwise indicated by a modifying term, such as immature neutrophil; any cell or tissue that manifests no special affinity for acid or basic dyes, i.e. the cytoplasm stains approximately equally with either type of dye

nongranular leukocytes: a general, nonspecific term frequently used with reference to lymphocytes, monocytes, and plasma cells; although the cytoplasm of a lymphocyte or monocyte contains tiny granules, it is nongranular in comparison with that of a neutrophil, basophil, or eosinophil


oliguria: scanty urine production

osmol gap: the difference between the measured osmolality and the calculated osmolality

osmolality: the concentration of a solution expressed in osmoles of solute particles per kilogram of solute


pancytopenia: pronounced reduction in the number of erythrocytes, all types of white blood cells, and the blood platelets in the circulating blood

paraprotein: a monoclonal immunoglobulin of blood plasma, observed electrophoretically as an intense band in γ, β, or α regions, due to an isolated increase in a single immunoglobulin type as a result of a clone of plasma cells arising from the abnormal rapid multiplication of a single cell; the finding of a paraprotein in a patient’s serum indicates the presence of a proliferating clone of immunoglobulin-producing cells and may be seen in a variety of malignant, benign, or non-neoplastic diseases

pharmacogenetics: the study of genetically determined variations in responses to drugs in humans or in laboratory organisms

positive predictive value: the fraction of positive values which are correct; determined by dividing the true positives by the sum of the true positives and false positives

precision: the closeness of scatter in multiple measurements of the same quantity


red blood count (RBC): Calculation of the number of red blood cells (RBC) in a cubic millimeter of blood, by means of counting the cells in an accurate volume of diluted blood

reference range: the inner 95% of values for a laboratory test as measured in a defined population; the subject population is typically disease free with regards to the test of interest

respiratory acidosis: acidosis caused by retention of carbon dioxide; due to inadequate pulmonary ventilation or hypoventilation, with decrease in blood pH unless compensated by renal retention of bicarbonate

respiratory alkalosis: alkalosis resulting from abnormal loss of CO2 produced by hyperventilation, either active or passive, with concomitant reduction in arterial plasma bicarbonate concentration


sarcoma: a connective tissue neoplasm, usually highly malignant, formed by proliferation of mesodermal cells

sensitivity: the proportion of affected individuals who give a positive test result for the disease that the test is intended to reveal; (true positive results divided by total true positive and false negative results)

specificity: true negative results as a proportion of the total of true negative and false positive results

standard deviation: statistical index of the degree of scatter from the central tendency, namely, of the variability within a distribution


T cell lymphocyte: a thymocyte-derived lymphocyte of immunologic importance that is long-lived (months to years) and is responsible for cell-mediated immunity; T lymphocytes form rosettes with sheep erythrocytes and, in the presence of transforming agents (mitogens), differentiate and divide; these cells have characteristic CD3 surface markers and may be further divided into subsets according to function, such as helper, cytotoxic etc.

thalassemia: any of a group of inherited disorders of hemoglobin metabolism in which there is impaired synthesis of one or more of the polypeptide chains of globin; several genetic types exist, and the corresponding clinical picture may vary from barely detectable hematologic abnormality to severe and fatal anemia

thrombocytopenia: a condition in which there is an abnormally small number of platelets in the circulating blood

thromobocyte: platelet; an irregularly shaped disk-like cytoplasmic fragment of a megakaryocyte that is shed in the marrow sinus and subsequently found in the peripheral blood, where it functions in clotting; a platelet contains granules in the central part (granulomere) and, peripherally, clear protoplasm (hyalomere), but no definite nucleus; is about one-third to one-half the size of an erythrocyte; and contains no hemoglobin

thyroditis: inflammation of the thyroid gland

thyrotropin releasing hormone (TRH): abbreviation for thyrotropin-releasing hormone

thyrotropin: a glycoprotein hormone produced by the anterior lobe of the hypophysis that stimulates the growth and function of the thyroid gland; it also is used as a diagnostic test to differentiate primary and secondary hypothyroidism

thyroxine: the l-isomer is the active iodine compound existing normally in the thyroid gland and extracted there from in crystalline form for therapeutic use; also prepared synthetically; used for the relief of hypothyroidism, cretinism, and myxedema

total iron binding capacity (TIBC): the capacity of iron-binding protein in serum (transferrin) to bind serum iron

toxicology: the science of poisons, including their source, chemical composition, action, tests, and antidotes

transferrin: a nonheme β1-globulin of the plasma, capable of associating reversibly with up to 1.25 μg of iron per gram, and acting therefore as an iron-transporting protein

triglycerides: glycerol esterified at each of its three hydroxyl groups by a fatty acid

triiodothyronine: a thyroid hormone normally synthesized in smaller quantities than thyroxine; present in blood and thyroid gland and exerts the same biologic effects as thyroxine but, on a molecular basis, is more potent and the onset of its effect is more rapid

tumor: any swelling or tumefaction

thyroid stimulation hormone (TSH): see thyrotropin


urea: the chief end product of nitrogen metabolism in mammals, formed in the liver by means of the Krebs-Henseleit cycle and excreted in normal adult human urine in the amount of about 32 g a day


vitamin B12: generic descriptor for compounds exhibiting the biological activity of cyanocobalamin (cyanocob(III)alamin); the antianemia factor of liver extract that contains cobalt, a cyano group, and corrin in a cobamide structure; the physiologically active vitamin B12 coenzymes are methylcobalamin and deoxyadenosinecobalamin; a deficiency of vitamin B12 is often associated with certain methylmalonic acidurias

Von Willebrand’s disease: a hemorrhagic diathesis characterized by tendency to bleed primarily from mucous membranes, prolonged bleeding time, normal platelet count, normal clot retraction, partial and variable deficiency of factor VIIIR, and possibly a morphologic defect of platelets; autosomal dominant inheritance with reduced penetrance and variable expressivity, caused by mutation in the von Willebrand factor gene (VWF) on 12p; type III von Willebrand’s disease is a more severe disorder with markedly reduced factor VIIIR levels; there is a recessive version of this disease [MIM*277480] which has the remarkable property that it represents a mutation at the same locus as the dominant form


white blood count (WBC): calculation of the number of white blood cells (WBC) in a cubic millimeter of blood, by means of counting the cells in an accurate volume of diluted blood

Wilson’s disease: a disease caused by a defect in copper metabolism, leading to deposition of copper in liver, brain, kidney and other tissues; characterized by cirrhosis of the liver and degenerative changes in the brain


Zollinger Ellison syndrome: a peptic ulceration with gastric hypersecretion and gastrinoma of the pancreas or duodenum, sometimes associated with familial multiple endocrine adenomatosis type 1

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