Biochemistry test profile



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BIOCHEMISTRY TEST PROFILE:

The serum biochemistry profile measures a variety of chemicals and enzymes (proteins that are involved in the body’s chemical reactions) in the blood to provide very general information about the status of organ (especially the liver, kidneys, and pancreas) health and function. The biochemistry profile also shows the patient’s blood sugar level and the amounts of important electrolytes (molecules like sodium, calcium, and potassium) in the blood.

Serum biochemistry values that help provide information about the liver include the ALKP (alkaline phosphatase), ALT (alanine aminotransferase), AST (aspartate aminotransferase), and TBIL (total bilirubin).


  • Serum biochemistry values that help evaluate the kidneys include the BUN (blood urea nitrogen) and CREAT (creatinine).

  • AMYL (amylase) and LIP (lipase) are enzymes produced by the pancreas.

  • Electrolytes are checked for quantity and for proportion to other electrolytes. They include Ca (calcium), Cl (chloride), K (potassium), Na (sodium), and PHOS (phosphorus.) Electrolyte abnormalities can be associated with many types of health issues.

LIVER FUNCTION TEST

FUNCTIONS OF LIVER:

1.Metabolic function: Liver actively participate in carbohydrate,lipid,protein,mineral and vitamin metabolism.

2.excretory function;bile pigments,bile salts,and cholesterol are excreted in the bile into intestine.

3.protective function and detoxification:kupffer cells of liver cells perform phagocytosisto eliminate forign compounds.Ammonia is detoxified to urea.liver is responsible for the metabolism of detoxification.

4.Hematological function:liver participates in the formation of blood,synthesis of plasma proteins,and destruction of erythrocytes.

5.Storage function:Glycogen,vitamin A,D and B12 and trace elementiron are stored in the liver.



Liver function test includes:

Sr.bilirubin,SGPT,SGOT,ALP,sr.protein,(albumin and globulin),urine:bile salt,bile pigment,urobilinogen.



Sr.bilirubin:

Bilirubin is the excretory end product formed by the catabolism of heme.it is conjugated by the liver to form bilirubin diglucuronide and excerted through bile.



  • Normal sr.bilirubin level varies from 0.2 to 0.8 mg/dl.The unconjugated bilirubin varies from 0.2-0.6mg/dl and conjugated bilirubin 0.0-0.2 mg/dl.A rise in serum serum nbilirubin above 1 mg% is abnormal,but jaundice appears only if the level goes to 2.0 mg%.

  • The bilirubin estimated by van den bergh reaction,diazotized sulfanilic acid reacts with bilirubin to form a purple colour complex called Azobilirubin.normal sr. does not give the positive reaction.

  • When bilirubin is conjugated,the purple colour produced immediately on mixing with the reagent, the response is said to be Van den bergh direct positive.

  • When the bilirubin is uncojugated,the colour is obtained only when alcohol is added,and this response is known as Indirect Positive.

Sr. enzymes derived from liver

Transaminases or aminotransferases

  • The activity of two enzymes,namely sr,glutamate pyruvate trans aminase (SGOT/ALT-Alanine trans aminase)and sr.glutamate oxaloacetate transaminase(SGPT/AST-Aspartate trasaminase)- are widely used to asses the function of liver.

  • ALT is acytoplasmic enzyme while AST is found in both cytoplasm and mitochondria.

  • ALT:5-35u/l,AST: 5-35u/l.

  • ALT is more senstitive and reliable for the assessment of LFT.

Alkaline phopatases:

  • ALP is mainly derived from bone and liver.A rise in sr.ALP,usually associated with sr.bilirubinis an indicator of bilary obstruction.ALP is also elevated in cirrhosis of liver and hepatic jaundice.(range 40-125IU/L)

Glutamyl trans peptidase

  • Measurement of GGT is highly elevated in biliary obstruction and alcoholism and it provides sensitive index to asses liver abnormality.(range10-30 IU/L)

SERUM ALBUMIN

  • Albumin is solely synthesized in liver.It has a half life of about 20-25 days btherfore,it is a good marker to asses the chronic liver damage.low sr.Albumin is commonly observed in patients with severe liver damage.

  • Cirrhosis of liver causes a reversal of albumin/globulin ratio(A/G ratio).

Urine analysis

Bile salt:

  • Bile salt consist of glycocholic acid and taurocholic acid.they lower the surface tension of the fluid and thus cause sulphur particles to sink

  • Take about 3-5 inch coloumn of urine in small beaker or in a test tube.sprinkle finely powered dry sulfur over the surface from height of about half-inch.if bile salts are present,the sulfur powder will sink at bottom.

  • The presence of bile salts indicates obstructive jaundice.

Bile pigment:

  • Fouchets test: This is most sensitive test.if the urine ias alkaline or neutral,acidify it with few drops of 2 drops of acetic acid.

  • To 10 ml of acidic urine add about 5 ml of 10% barium chloride solution.mix well and filter.to the residue on the filter paper add a drop of fouchets reagent.

  • A green or blue colour indicatespresence of of bile pigments i.e. biliverdin and bilirubin respectively.

Urobilinogen:

  • If the urine sample contains bile pigment it should be removed by addition of 1 part of 10% aqueous solution of calcium chloride to 4 parts of urine and filter it.

  • To 10 ml of fresh urine,add 1 ml of Ehrlich aldehyde reagent.Allow it to stand for 3 min.if red/cherry colour is obtained,it indicates presence of urobilinogen.

JAUNDICE

Definition:

  • Jaundice is clinical condition characterized by yellow colour of the white of the eyes(sclera) and skin.

  • It caused by the deposition of bilirubin due to its elevated levels in the serum.

  • The term Hyperbiliubinemia is used to represent the increased concentration of bilirubin.

Classification of jaundice

  • Jaundice is classified into three major types:

  • Hemolytic jaundice: this condition is associated with increased hemolysis of erythrocytes.e.g . incompatible blood transfusion,malaria,sickle cell anemia).this result in the over production of bilirubin beyond the ability of the liver to conjugate and exceate the same.

  • Elevation in the sr.uncojugated bilirubin.

  • Hepatic jaundice: it is caused by dysfunction of th liver due damage to the parenchymal cells.this may be attributed to viral infection,poisons and toxins.

  • Damage to the liver adversely affects the bilirubin ubtake and its conjugation by liver cells.its characterized by

  • Inceased levels of conjugated and unconjugated bilirubin in the serum.

  • Increased activities of sr.ALT and AST.

  • Obstructive jaundice:this is due to an obstruction in the bile duct that prevents passage of bile into intestine.the obstruction may be caused by gall stones,tumors etc.

  • Due to blockage in bile duct,the unconjugated bilirubin from the liver entes the circulation.its characterized by

  • Increased concentration of conjugated bilirubin in serum.sr.ALP is also elevated.

KIDNEY(RENAL) FUNCTION TESTS

The kidney are the vital organs of the body, performing the following major function.



  • Maintenance of homeostasis:the kidneys are largely responsible for the regulation of water,electrolyte and acid-base balance in the body.

  • Excreation of metabolic waste products: the end products of protein and nucleic acid metabolism are eliminated from the body.these include urea,creatinine,uric acid,sulfate and phosphate.

  • Retension of substances vital to body: the kidneys reabsorb and retain several substances of biochemical importance in the body.e.g.glucose,aminoacids etc.

  • Hormonal function: the kidneys also function as endocrine organs by producing hormonese.g.erythropoietin,calcitriol.

Formation of urine:

  • Nephron is the functional unit of kidney.each kidney is composed of approximately one million nephron.

  • nephron consists of bowman’s capsule,proximal convoluted tubule,loop of henle,distal convoluted tubule and collecting tubule.

  • The blood supply to kidney isrelatively large.about 1200 ml of blood(650 ml of plasma)passes through the kidneys,every minute.

  • From this ,about120-125 ml filtered per minute by the kidneys and this is referred to as Glomerular filtration rate(GFR).

  • With a normal GFR,the glomerular filtrate formed in an adult is about 175-180 litres per day,out of which only 1.5 litres is excreated as urine.thus more than 99% of glomerular filtrate is re absorbed by the kidneys./

TESTS TO ASSESS RENAL FUNCTION

  • The kidney function test may be divided intofour groups:

  • Glomerular function test:

  • All the clearance tests are included in this group.

  • Clearance tests: it is defined as the volume of plasma that would be completely cleared of a substances per minute.

  • Clearance (C),expressed as ml/min,can be calculated by using the formula

U x V

C = -------

P

Where U = concentration of the substance in urine.



V = volume of urine in ml excreated per minute.

P = concentration of the substance in plasma.



  • Creatinine clearance test: it is an excreatoryb product derived from creatine phosphate.the excreation of creatinine is rather constant and is not influenced by body metabolism or dietary factors.

  • Creatinine clearance may be defined as the volume of plasma that would be compleately cleared of creatinine per minute.

  • Normal range – 120-145 ml/min.

  • A decrease in creatinine clearance (<75% normal) serve as sensitive indicator of a decreased GFR,due to renal damage.

Urea clearance test :

  • It is rhe end product of protein metabolism.after being filtered by the glomerulai,it is partially reabsorbed by the renal tubules.hence urea clearance is less than the GFR and further it is influenced by the potein content of the diet.for this reason urea clearance is not as sensitive as creatinine clearance.

Lipid profile

  • Lipids are a group of fats and fat-like substances that are important constituents of cells and sources of energy. A lipid profile measures the level of specific lipids in the blood.

  • Two important lipids, cholesterol and triglycerides, are transported in the blood by lipoprotein particles. Each particle contains a combination of protein, cholesterol, triglyceride, and phospholipid molecules. The particles measured with a lipid profile are classified by their density into high-density lipoproteins (HDL), low-density lipoproteins (LDL), and very low-density lipoproteins (VLDL).

  • Cholesterol:cholesterol is amphipathic in nature,since it possesses both hydrophilic and hydrobhobic regions in the structure.about 1 g of cholesterol is synthesized per day in aults.almost all tissues of the body participate in cholesterol biosynthesis.the largest contribution is made by liver(50%),intestine(15%),skin,adrenal,cortex etc.

  • Plasma cholesterol is associated with different lipoprotein fraction(LDL,VLDL,HDL).

  • Triglycerids:it is the most abundant lipids comprising 85-90%of body lipids.most of the TGL are stored in adipose tissue and serves as energy reserve of the body.

  • In total plasma lipid ,one third is cholesterol,one third is tgl and one third is phopholipid.since lipids are insoluble in water,they need the help of carriers in plasma.therfore they are complexed with proteins to form lipoproteins.the protein part of lipoprotein is called apolipoprotein.

  • Lipoproteins: depending upon the density (by ultracentrifugation) or on the electrophoretic mobility,the Lp in plasma are classified in to five major types.They function as transport vehicles for lipids in blood plasma.Lp deliver the lipid components (cholesterol,TGL etc) to various tissues for utilization.

1.chylomicrons.

2.very low density lipoprotein(VLDL)

3.Intermediate density lipoprotein(IDL)

4.low density lipoprotein(LDL)

5.High density lipoprotein(HDL).

1.chylomicrons: they are synthesized in the intestine and transport exogenous (dietary)tgl to various tissues.

2.VLDL:they are produced in liver and intestine and are responsible for the transport of endogenously synthesized TGL.

3.LDL:they are formed from VLDL in the blood circulation.they transport cholesterol from liver to othe tissues.

4.HDL:they are mostly synthesized in liver.hdl particles transport cholesterol from peripheral tissues to liver.

Bad cholesterol and Good cholesterol:


  • The cholesterol in high concentration,present in ldl,is considered bad cholesterol due to its involvement in altherosclerosis and related complication.

  • On the other hand HDL is good since its high concentration counteracts atherogenesis.

Clinical significance:

  • Hypercholesterolemia is associated with athrosclerosis and coronary heart disease.consumption of poly unsaturated fatty acids and fiber decreases cholesterol in circulation.

  • Excessive accumulation of TGL causes fatty liver which can often be prevented by the consumption of lipoprtic factors.

  • Obesity is an abnormal increase in body weight due to excessive fat deposition.overeating,lack of exercise and genetic predisposition play a significant role in the development of obesity.

THYROID FUNCTION TESTS

Hormones: Hormones are defined as organic substances,produced in small amounts by specific tissues(endocrine glands),secertedin to the blood stream to control the metabolic and biological activities in the target cells.

Classification of Hormones:

  • Based on the chemical nature:

1.Protein or peptide hormones e.g. insulin,glugacon,antidiuretic hormone,oxytocin.

2.Steroid hormones e.g.glucocorticoids,mineralocarticoids,sex hormones.

3.Amino acid derivatives e.g.epinephrin,nor epinephrine,thyroxin(T4),Triiodothyronin(T3).


  • Based on the mechanism of action:

  • Hormones are classified into two broad groups(I &II) based on the location of the receptors to which they bind,and the signals used to mediate their function.

  • Group I hormones:these hormones bind to intracellular receptors to form receptor-hormone complexes through which their biochemical functions are mediated.group I hormones are derivatives of cholesterol.e.g. estrogens,androgens, glucocorticoids,calcitriol.

  • Group II hormones:these hormones bind to cell surface(plasma membrane) receptors and stimulate the release of certain molecules,namely the Second messengers.

  • Group II hormones are subdivided into three categories based on the chemical nature of the second messengers.

a)the second messenger is cAMP e.g.ACTH,FSH,LH,PTH,glucagon,calcitonin.

b)the second messenger is phophotidyl-inositol/calcium e.g.TRH,GnRH,Gastrin.

c)the second messenger is unknown e.g.growth hormone,insulin,oxytocin,prolactin.

THYROID HORMONES



  • Thyroid gland (weighs about 30g in adults)is located either side of the trachea below the larynx

  • It produces twom principle hormones –thyroxine and triiodothyronin which regulate the metabolic rate of the body.

  • Iodine is essential for the synthesis of thyroid hormones.more than half of the body’s total iodine content is found in the thyroid gland,

  • FUNCTIONS OF THYROID HORMONES

1.Influence on the metabolic rate:thyroid hormones stimulate the metabolic activities and increase the oxygen consumption in most of the tissues(exception-brain,lungs,tests and retina)

2.effect on protein synthesis:thyroid hormones act like steroid hormones in promoting protein synthesisby actinf at the transcriptional level (activate DNA to produce RNA)

3.Influence on the carbohydrate metabolism:thyroid hormones promote intestinal absorbtion of glucose and its utilization.

4.effect on lipid metabolism:lipid turnover and utilaisation are stimulated by thyroid hormones.Hypothyroidism is associated with elevatedplama cholesterol level which can be reversed by the administration of thyroid hormone.

TSH:


  • . Thyroid-stimulating hormone (also known as thyrotropin, thyrotropic hormone, TSH, or hTSH for human TSH) is a pituitary hormone that stimulates the thyroid gland to produce thyroxine (T4), and then triiodothyronine (T3) which stimulates the metabolism of almost every tissue in the body.[1] It is a glycoprotein hormone synthesized and secreted by thyrotrope cells in the anterior pituitary gland, which regulates the endocrine function of the thyroid.

  • T3 and T4

  • The thyroid hormones, triiodothyronine (T3) and its prohormone, thyroxine (T4), are tyrosine-basedhormones produced by the thyroid gland that are primarily responsible for regulation of metabolism. T3and T4 are partially composed of iodine (see molecular model). The major form of thyroid hormone in the blood is thyroxine (T4), which has a longer half-life than T3.

  • T4 is converted to the active T3 (three to four times more potent than T4) within cells by deiodinases (5'-iodinase). These are further processed by decarboxylation and deiodination to produce iodothyronamine (T1a) and thyronamine (T0a). All three isoforms of the deiodinases are selenium-containing enzymes, thus dietary selenium is essential for T3 production.

Abnormalities of thyroid function:

GOITER:


  • Any abnormal increase in the size of the thyroid gland is known as goiter.enlargement of thyroid gland is mostly compensate the decreased synthesis of thyroid hormones and its associated with elevated TSH.

  • Simple endemic goiter: this is due to iodine deficiency in the diet.

  • Hyperthyroidism: this is also known as throtoxycosis and is associated with over production of thyroid hormones.it is characterized by increased metabolic rate,nervousness,irritability,anxiety,rapid heart rate,loss of weight despite increased appetite,weakness,diarrhea,sweating.sesitivity to heat and often protrution of eye balls.

ENZYMES

Definition: enzymes are biocatalysts-the catalysts of life.A catalyst is defined as substance that increases the velocity or rate of chemical reaction without itself undergoing anyother changes in the overall process.



  • Classification of enzyme:

1.Oxidoredutases:enzymes involved in oxidation-reduction reaction e.g.alcohol dehydrogenase.

2.Transferases:enzymes that catalyse the transfer of functional groups.e.g hexokinase.

3.Hyrdrolases:enzymes that bring about hydrolysis of various compounds e.g.lipase.

4.lyases;enzymes specialized in the addition or removal of water,ammonia,CO2 .e.g.aldolase.

5.Isomerases:enzymes involved in all the isomerization reaction e.g.phosphohexose isomerase.

6.ligases:enzymes involved in all the isomerization reaction.g.phosphohexose isomerase.



  • Active site: the active site of an enzyme is defined as the small region at which the substrates bind and participates in the calalysis.

  • Salient features of active site:

1.the active site is made up of amino acids(known as catalytic residues) which are far from each other in the linear sequence of aminoacidsfor instance,the enzyme lysozyme has 129 amino acid residues numbered 35,52,62,63 and 101.

2.the active site is not regid in structure and shape.it is rather flexible to promote the specific substrate binding.

3.generally,the active site possesses a substrate bindin site and a catalytic site.the latter is for the catalysis of the specific reaction.


  • Coenzymes;

  • many enzymes require certain non protein small additional factors,collectively referred to as cofactors for catalysis.the co factors may be organic or in organic in nature.

  • The non-protein,organic,low molecularweight and dialyzable substances associated with enzyme function is known as coenzyme.

  • The function enzyme referred asto as holoenzyme which is made up of a protein part (apoenzyme) and a non protein part(coenzyme).

  • The term activator is referred to the inorganic cofactors (like Ca2+,Mg2+,etc)necessary to enhance enzyme activity

Sr.AMYLASE

  • Sr.Amylase: Amylase is an enzyme, or special protein, produced by pancreas and salivary glands. The pancreas is an organ located behind stomach. It creates various enzymes that help break down food in intestines.

  • The pancreas can sometimes become damaged or inflamed, which causes it to produce too much or too little amylase. An abnormal amount of amylase in body may be a sign of a pancreatic disorder.

  • An amylase blood test can determine whether a disease of the pancreas by measuring the amount of amylase in body. You may have a disorder affecting the pancreas if the levels of amylase are too low or too high.

  • Amylase is typically measured by testing a sample of your blood. In some cases, a urine sample may also be used to determine the amount of amylase in your body.

  • An amylase blood test is usually done if your doctor suspects a pancreatic disorder, such as pancreatitis,pancreatic cancer, or gallstones. Symptoms vary for the different diseases, but they may include: severe abdominal pain,loss of appetite,fever,nausea.


SGOT

SGOT: Serum glutamic oxaloacetic transaminase, an enzyme that is normally present in liver and heart cells. SGOT is released into blood when the liver or heart is damaged. The blood SGOT levels are thus elevated with liver damage (for example, from viral hepatitis) or with an insult to the heart (for example, from a heart attack). Some medications can also raise SGOT levels. SGOT is also called aspartate aminotransferase (AST).

Aspartate transaminase catalyzes the interconversion of aspartate and α-ketoglutarate to oxaloacetate and glutamate.



Aspartate (Asp) + α-ketoglutarate ↔ oxaloacetate + glutamate (Glu)

Reaction catalyzed by aspartate aminotransferase

As a prototypical transaminase, AST relies on PLP (Vitamin B6) as a cofactor to transfer the amino group from aspartate or glutamate to the corresponding ketoacid.

AST is similar to alanine transaminase (ALT) in that both enzymes are associated with liver parenchymal cells. The difference is that ALT is found predominantly in the liver, with clinically negligible quantities found in the kidneys, heart, and skeletal muscle, while AST is found in the liver, heart (cardiac muscle), skeletal muscle, kidneys, brain, and red blood cells.[20] As a result, ALT is a more specific indicator of liver inflammation than AST, as AST may be elevated also in diseases affecting other organs, such as myocardial infarction, acute pancreatitis, acute hemolytic anemia, severe burns, acute renal disease, musculoskeletal diseases, and trauma.



SGPT

ALT is found in plasma and in various body tissues, but is most common in the liver. It catalyzes the two parts of the alanine cycle.ALT catalyzes the transfer of an amino group from L-alanine to α-ketoglutarate, the products of this reversible transaminationreaction being pyruvate and L-glutamate.

L-glutamate + pyruvate ⇌ α-ketoglutarate + L-alanine



Alanine transaminase

ALT (and all transaminases) require the coenzyme pyridoxal phosphate, which is converted into pyridoxamine in the first phase of the reaction, when an amino acid is converted into a keto acid.

ALT is commonly measured clinically as a part of a diagnostic evaluation of hepatocellular injury, to determine liver health.

Lactate dehydrogenase .

Lactate dehydrogenase (LDH or LD) is an enzyme found in nearly all living cells (animals, plants, and prokaryotes). LDH catalyzes the conversion of lactate to pyruvic acid and back, as it converts NAD+ to NADH and back. A dehydrogenase is an enzyme that transfers a hydride from one molecule to another.

LDH is expressed extensively in body tissues, such as blood cells and heart muscle. Because it is released during tissue damage, it is a marker of common injuries and disease such as heart failure.




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