Oral Glucose Tolerance Test

Laboratory Exercise Objectives To determine the array of the test that should be

performed on the patient To further identify the particular normal values

that are standard for each test To compare the standard normal values with the

obtained laboratory results To establish expected laboratory values To understand why these laboratory test was

chosen for these specific patient.

Experiment Objective To be familiar with the normal values of

blood sugar in the test To provide the significance of testing OGTT

in patients suspected with diabetes To be acquainted with other diseases that

can cause abnormal glucose tolerance test result

Case 50 year old 122 mg/dL plasma glucose Family history:

Two siblings with Type II Diabetes Mellitus

Sedentary lifestyle and rarely went to the gym

Oral Glucose Tolerance Test Sensitive Lack specificity Defines diabetes chemically Abnormal in many diseases Influenced by diet and other variables

Oral Glucose Tolerance Test Should be administered with in the

standard

Preparation Patient must be ambulatory and free from

illness or trauma Diet containing 150g of CHO for 3 days Advisable to do fasting blood glucose first

For three days prior to the test, the subject had a high carbohydrate diet of 300 gm per day

Eight hours before the test, on the day of the experiment, the subject had nothing by mouth.

Fasting blood sugar was taken using a glucometer.

The subject then ingested 75 gm glucose. Blood sugar was taken at 60 min, 90 min and 120

min after intake of glucose. The results were recorded.

High-Carbohydrate Preparatory Diet

The subject’s maximal ability to metabolize sugar is tested.

The repeated stimulation of postprandial hyperglycemia gradually restores maximal insulin responsiveness and reactivates the processes needed for disposal of glucose by different tissues.

RESULT

Result

105

110

115

120

125

130

135

140

145

60 mins 90 mins 120mins

Glucose level

60 mins= 142

90 mins= 124

120 mins=120

Normal values

AGE

(years)

SLIDING LIMIT

FIXED LIMIT

20 142 148

30 152 163

40 161 178

50 169 193

60 177 208

70 185 224

80 198 239

Proposed Age-Adjusted Normal Limits for Oral Glucose Tolerance Test

Blood sugar(mg/100 cc)

Normal Glucose ToleranceNormal Glucose Tolerance Plasma glucose levels below 140 mg/100cc both fasting and 2 hr after

glucose load

Impaired Glucose TransportImpaired Glucose Transport Requires a two hour plasma glucose level equal to or greater than 140

mg/100 cc but below 200 mg/100 cc and at least one value between 0 time and 2hr equal to or greater than 200 mg/100cc

Definite DiabetesDefinite Diabetes > Require either two fasting plasma glucose values 140 mg/100cc or

more; or a 2 hr plasma glucose level equal to or above 200 mg/100 cc, and at least one value between zero time and 2 hr equal to or greater than 200 mg/100 cc

ENDOCRiNE SYSTEM

PANCREAS

PANCREAS The pancreas is a

elongated organ, light tan or pinkish in color, that lies in close proximity to the duodenum. It is covered with a very thin connective tissue capsule which extends inward as septa, partitioning the gland into lobules.

PANCREAS The bulk of the

pancreas is composed of pancreatic exocrine cells and their associated ducts. Embedded within this exocrine tissue are roughly one million small clusters of cells called the Islets of Langerhans, which are the endocrine cells of the pancreas and secrete insulin, glucagon and several other hormones.

PANCREASPancreatic islets house

three major cell types:

Alpha cells (A cells) secrete the hormone glucagon.

Beta cells (B cells) produce insulin and are the most abundant of the islet cells.

Delta cells (D cells) secrete the hormone somatostatin, which is also produced by a number of other endocrine cells in the body.

INSULINa) stimulates liver, fat, and muscle cells to

take up glucose.

b) stimulates liver and muscles to store glucose as glycogen.

c) promotes buildup of fats and proteins and inhibits their use as an energy source.

INSULIN SYNTHESIS

Insulin gene encodes for preproinsulin.

Preproinsulin contains 4 sequential peptides: N-terminal

signal peptide

B chain C peptide A chain

The N-terminal signal peptide is degraded during the course of completion of the proinsulin molecule.

The proinsulin is folded into a conformation that permits the disulfide linkages between the A and B chains to form.

Converting enzymes cleave off the C peptide.

Insulin synthesis is completed

INSULIN SECRETION

1

34

3

5

7

6

8

2

9

1

2

3 4

5

6

7

REGULATION OF INSULIN SECRETION

REGULATIONGLUCOSE,

AMINO ACIDS,FFA/KETOACIDS,

POTASSIUM

INSULIN

STIMULATES SECRETION

STIMULATES UPTAKE, METABOLISM, STORAGE

Biphasic response:

1. First phase or Immediate pulse or Initial response

1. Rapid release of preformed insulin

– Second phase or Prolonged response1. Rapid release of newly synthesized insulin

2. Slow removal of insulin substrate inhibiting further release

3. Different sensitivity

REGULATION Factors affecting insulin secretion

Stimulators Inhibitors

glucose secretin fasting interleukin-1protein CCK exercise pancreastatin ketoacids vagal activity somatostatin leptinFFA Ach galaninpotassium glucagon endurance trainingcalcium GLP-1 -adrenergic activityGIP diazoxide-Adrenergic activity prostaglandin E2sulfonylurea drugsmeglitinides

INSULIN ACTION INSULIN RECEPTOR

composed of two alpha subunits and two beta subunits linked by disulfide bonds

alpha chains are entirely extracellular and house insulin binding domains

linked beta chains penetrate through the plasma membrane

INSULIN ACTIONInsulin binds to receptorsInsulin binds to receptors

Activates tyrosine kinaseActivates tyrosine kinase

autophosphorilationautophosphorilation

Fully activates tyrosine kinaseFully activates tyrosine kinase

Serine and threonine phosporilationSerine and threonine phosporilation

Activation of phosphatidylinositolGrowth receptor binding protein 2

Generates phosphatidylinositol-3-4 And 3,4,5 phosphates

Activates glycogen synthase,Signals mitogen-activated

Protein (MAP) kinase

2nd messengers2nd messengers

↓ cAMP levels↓ cAMP levels

Activation of glucose transport systemGLUT-4 (for muscle and adipose tissue)

Activation of glucose transport systemGLUT-4 (for muscle and adipose tissue)

Glucose → glycogen → pyruvate → lactate → fatty acids Glucose → glycogen → pyruvate → lactate → fatty acids

INSULIN ACTION

INSULIN ACTION

lipogenesis

lipolysis

glycogenesis

glycolysis

ketogenesis

glycogenolysis

glycogenesis

gluconeogenesis

protein synthesis

proteolysis

Synthesized by the alpha cells of the islets of Langerhans from a preproglucagon precursor when the blood glucose concentration falls

Functions to increase blood glucose concentrations

It is known as a hyperglycemic hormone

It is a primary hormone that regulates hepatic glucose production and ketogenesis

Its activities are affected by glucose concentration and insulin

Liver – major site of glucose degradation

Increased blood glucose inhibits glucagon secretion

• Decreased in blood glucose levels from normal (90 mg/100 ml), increases plasma concentration of glucagon (hypoglycemic)

• Increased blood glucose levels, decreases plasma glucagon (hyperglycemic)

Increased blood amino acids stimulates glucagon secretion

• High conc. of amino acids (esp. alanine & arginine), stimulate secretion of glucagon

• In this instance, glucagon and insulin responses are not opposites

• Glucagon promotes rapid conversion of amino acids to glucose making it more available to tissues

Exercise stimulates glucagon secretion

• Glucagon increases fourfold to fivefold during exhaustive exercise

Fasting for several days stimulates glucagon secretion

Vagal stimulation and acetylcholine release

It can be suppresses or inhibited by:

• glucose

• fatty acids

• GLP-1 and secretin

• somatostatin (inhibits release)

• breakdown of liver glycogen (Glycogenolysis)

• increased Gluconegenesis in the liver

Glucagon

Adenylyl cyclase

cAMP

Protein kinase

Glycogen Phosphorylase A Glycogen Phosphorylase B

Glucose-1-phosphate

(active) (inactive)

Phosphatase activity

Kinase activity

Glucagon phosphorylates

Fructose-6-P

Insulin dephosphorylates

Glucose

Pyruvate

6 Phosphofructokinase

Fructose-6-P

Fructose 2,6-P2

Fructose 1,6 biphosphatase

If increased

If decreased

Fructose 1,6-P2

Glucagon

FFA

Triglyceride Synthesis

Beta oxidation

Malonyl CoA

Carnitine acyltransferase

Acetyl CoA carboxylase

Acetyl CoAIncreases lipolysis and delivery of FFA

to the liver

Beta oxidation

HMG-CoA reductase

Adipose tissue lipase

Decreases cholesterol synthesis

• It is produced by the delta cells of islets of Langerhans

• It inhibits insulin and glucagon secretion

• It is stimulated by:

• increased blood glucose

• increased amino acids

• increased fatty acids

• increased concentrations of several of the GIT hormones

• Inhibitory effects:

• Acts in the islet of Langerhans to depress both insulin and glucagon

• Decreases motility of the stomach, duodenum and gallbladder

• Decreases secretion and absorption in the GIT

• Principal role: it extends the period of time over which the food nutrients are assimilated in the blood

• Decreases the utilization of the absorbed nutrients by the tissues, thus preventing rapid exhaustion of the food and therefore making it available over a longer period of time

It is described as having a blood glucose level that is higher than normal, but not high enough to be classified as diabetes

It is also been referred to as borderline or chemical diabetes or ‘pre-diabetes’

It carries a high risk of progressing to type 2 diabetes

It is combination of impaired secretion of insulin and reduced insulin sensitivity (insulin resistance)

It is also characterized by hyperglycemia

It exists if the fasting plasma glucose level is <140 mg/dl

It exists if the 30-, 60- and 90-minute plasma concentration is >200 mg/dl with a 2-hour plasma glucose level between 140 and 200 mg/dl

People who have a higher risk of developing IGT are:

those overweight

those with a family history of diabetes

women who have had gestational diabetes

those having hypertension or abnormal lipid profile

high LDL-cholesterol (also called "bad" cholesterol)

low HDL-cholesterol (also called "good" cholesterol)

Risks associated with IGT:

•Increased risk of heart attack

•Coronary artery disease, hypertension

•Onset of Type 2 diabetes

Nondiabetic causes

Liver cell disease

Chronic illness, prolonged physical inactivity

Acute stress state

Starvation, malnutrition

Potassium depletion

Diseases of other Endocrine glands

Acromegaly

Islet cell tumors

Pheochromocytoma

Drugs that alter Glucose Tolerance

A. Drugs that raise blood sugar

Chronic glucocorticoid administration

Oral diuretic compounds

Estrogen

Nicotinic acid

B. Drugs that lower blood sugar

Salicylates

Monoamine-Oxidase inhibitors

• following a healthy balanced diet

• weight control

• exercise

• glucose monitoring

• blood pressure monitoring

Fasting Blood Glucose Test

Oral Glucose Tolerance Test

Postprandial Blood Glucose Test

DIABETES MELLITUS

What is it?

- Diabetes mellitus is a group of metabolic diseases characterized by high blood sugar (glucose) levels, which result from defects in insulin secretion, or action, or both.

DIABETES MELLITUS

What causes it?

- Insufficient production of insulin (either absolutely or relative to the body's needs), production of defective insulin (which is uncommon), or the inability of cells to use insulin properly and efficiently leads to diabetes.

DIABETES MELLITUS

What are the types?

► Type I DM – insulin dependent

► Type II DM – non-insulin dependent

DIABETES MELLITUS TYPE I DM

- Type IA DM results from beta cell destruction that usually leads to insulin deficiency, while for the Type IB DM lack immunologic markers.

- major susceptibility gene for type IA is located in chromosome 6, HLA region.

- classically occurs in juvenile but can occur at any age

DIABETES MELLITUS Type I DM

- had classic symptoms of diabetes called “ 3 polys” that is associated with weight loss: polyphagia(derire to aet a lot or sugar craving), polydipsia(desire to drink water at all time) and polyuria(have to urinate frequently).

- prone to ketosis due to reduced insulin level, could lead to an increase in lipolysis and release of free fatty acids.

DIABETES MELLITUS Type II DM

- Defect in insulin receptors in insulin targets cells

- Patients are usually obese/overweight- Stronger genetic basis

- Non-ketosis prone - Usually occurs at age 40 or over

DIABETES MELLITUS Type II DM

- 3 pathophysiologic abnormalities: Insulin resistance – decreased ability of insulin

to act effectively on peripheral target tissues. Impaired insulin secretion – endogenous

production continues, but the amount secreted is less than the normal at same plasma glucose concentration.

Increased hepatic glucose production – failure of hyperinsulinemia to suppress gluconeogenesis

Other Laboratory Procedures

For Diabetic screening and diagnosis

Criteria for Diagnosis

Symptoms of diabetes plus random/casual blood glucose concentration greater than or equal to 11.1 mmol/L or 200mg/dL.

Fasting plasma glucose greater than or equal to 7 mmol/L or 126mg/dL.

Two-hour plasma glucose greater than or equal to 11.1 mmol/L or 200 mg/dL during an OGTT.

Criteria for DiagnosisBased on the following premises:

Spectrum of fasting plasma glucose and the response to an oral glucose load varies in normal individuals

DM defined as the level of glycemia at which diabetes-specific cimplications are noted and not the level of tolerance from a population based viewpoint

(reflects new epidemiologic and metabolic evidence as issued by National Diabetes Group and WHO; prevalence of retinopathy in Native Americans begins to increase at FPG >116 mg/dL)

Risk factors for DM type IIFamily history of diabetes (parent or sibling)Obesity (≥ 20% of desired body weight or BMI ≥ 27 kg/m2)Age ≥ 45 yearsRace/ethnicity (African American, Hispanic American, Native American, Asian American, Pacific Islander)History of GDM or delivery of baby over 9 lbs)HypertensionLow HDL cholesterol (≤0.90 mmol/L) levels and/or high triglyceride levels (≥ 2.82 mmol/L)Polycystic ovary syndrome

Diagnosis MethodDiagnosis of diabetes MUST be based on blood glucose estimations Urine glucose must not be the basis for diagnosisTrue blood glucose should be estimated using enzymatic methods (Glucose Oxidase method)Blood glucose estimation should be specified whether it has been carried out on capillary blood, whole venous blood, or on venous plasma OGTT in a known diabetic is not necessaryIn all other persons, an OGTT must be carried out in order to exclude diabetes

Fasting Plasma Glucoseits widespread use as a screening test is strongly encouraged because

(1) a large number of individuals ho meet the current criteria for DM are unaware that they have the disorder

(2) epidemiologic studies suggest that type 2 DM may be present for up to a decade before diagnosis

(3) as many as 50% of individuals with type 2 DM have one or more diabetes-specific complications at the time of their diagnosis

Fasting Plasma Glucoseafter the person has fasted overnight (at least 8 hours), a single sample of blood is drawn and sent to the laboratory for analysis

Venous blood glucoseNORMAL: ≤ 100 mg/dL

IFG: 100 ≥ 110 mg/dL

DIABETIC: ≥ 110 mg/dL

Capillary blood glucoseNORMAL: ≤ 100 mg/dL

IFG: 100 ≥ 110 mg/dL

DIABETIC: ≥ 110 mg/dL

Plasma venous blood glucoseNORMAL: ≤ 110 mg/dL

IFG: 110 ≥ 126 mg/dL

DIABETIC: ≥ 126 mg/dL

Fasting Plasma Glucoseusually preferred: easy to perform, faster, and more convenient for the patientunder-diagnoses the problem: normal FPG, but will have an elevated 2-hour PG first abnormality that occurs is the rise in post-prandial blood glucosefasting levels rise to abnormal values much lateron the basis of FPG alone, complications due to tissue damage might already be present before diagnosis

Random Blood Glucose Test random blood samples (if taken shortly

after eating or drinking) may be used to test for diabetes when symptoms are present

blood glucose level of 200 mg/dl or higher indicates diabetes

must be reconfirmed on another day with a fasting plasma glucose or an OGTT

Intravenous glucose tolerance test given to patients who are unable to tolerate a large carbohydrate load orally or who have altered gastric physiologysame preparation as with OGTT glucose solution is injected within a 3 to 4 minute interval and blood samples are obtained at 5-15 minute intervals over periods varying from 30-90 minutes after the injection glucose values are plotted and from the data, a removal rate constant is obtainedlower values indicate an abnormal tolerance to glucose loadOGTT curves that are flat (no rise greater than 20mg/dL) are observed as the results of various malabsorption syndromes, in this case the test is useful if the additional presence of diabetes is suspected

Urinalysisnot a reliable diagnostic tool but may be used in conjunction with blood glucose estimationpersons with no sugar in their urine, but very high blood sugar levelsless than 0.1% of glucose normally filtered by the glomerulus appears in urine (< 130 mg/24 hr)Glycosuria or Glucosuria

Urinalysiscopper reduction method: Benedict’s test

Highly non-specificCan give false positive results in the presence of other reducing agents

Appearance of reaction Report as Glucose equivalent (mg/dL)

Clear blue to turbid green 0 0-100

Green to yellow precipitate 1+ 100-500

Greenish yellow to yellow 2+ 500-1000

Orange or brown 3+ 1000-2000

Brick red 4+ Over 2000

enzymatic reduction method: Glucose oxidase strips

more specific but can give false negative results

results may be affected by ascorbic acid

PHYSICAL EXAMINATION AND RELATED TESTS

PHYSICAL EXAMINATION INSPECTION PALPITATION PERCUSSION AUSCULTATION LABORATORY TESTS SCREENING FOR DISEASE

WHAT TO CHECK FORVITAL SIGNS GENERAL APPEARANCE

HEENT CARDIOVASCULAR

RESPIRATORY CHEST

GENITOURINARY LYMPHATIC

MUSCULOSKELETAL SKIN

NEUROLOGIC PSYCHIATRIC

SUPPORTIVE TESTS FOR DM

BLOOD PRESSURE PERIPHERAL PULSES

ECG URINALYSIS

RESPIRATION RETINAL EXAMINATION

FOOT EXAMINATION NEUROLOGIC EXAMINATION

BLOOD PRESSURE & PERIPHERAL PULSESORTHOSTATIC Bp increase or decrease by 20mmHG

after standing for one minute against a supine Bp measurement.

LOOK FOR SIGNS OF IRREGULAR HEART BEATS

ECG1.       Abnormally fast or irregular heart rhythms. 2.       Abnormally slow heart rhythms. 3.       Abnormal conduction of cardiac impulses 4.       Evidence of the occurrence of a prior heart attack.5.       Evidence of an evolving, acute heart attack. 6.       Evidence of an acute impairment to blood flow to the heart. 7.       Adverse effects on the heart from various heart diseases or

systemic diseases. 8.       Adverse effects on the heart from certain lung conditions. 9.       Certain congenital heart abnormalities.

Evidence of abnormal blood electrolytes Evidence of inflammation of the heart or its lining

URINALYSISSPECIFIC GRAVITY GLUCONURIA

Ph ANTIBODIES

PROTEINURIA KETONURIA

ELECTROLYTES LEVEL

RESPIRATIONRESPIRATORY RATE

COMPENSATION

HISTORY OF SMOKING

RETINAL EXAMINATIONFLUORECEIN ANGIOGRAPHY

B-SCAN ULTRASOUND

FUNDUS PHOTOGRAPHY

Retinal photograph of a

patient complaining of

decreased vision.

Fluorescein angiogram

indicating fluid leakage within

the retina.

FOOT EXAMINATIONLOSS OF SENSATION

CHANGE IN SHAPE

FOOT ULCERS

NEUROLOGICAL TESTSSENSORY REFLEXES

COORDINATION & GAIT MOTOR

CRANIAL NERVES

MEDICAL HISTORY WEIGHT/BODY MASS INDEX FAMILY HISTORY & COMPLICATIONS CARDIOVASCULAR DISEASE MEDICAL CONDITIONS SMOKING EXERCISE

Genetic Considerations

Type I DM Genetic contributions involve multiple genes Development of the disease require inheritance of a sufficient

complement of genes to confer susceptibility Concordance in identical twins: 30-70%

Additional modifying factors must be present HLA complex polymorphisms – account for 40-50% of genetic

risk Region contain genes for class II MHC proteins (involved in

immune response; present antigen to helper T cells) Ability to present anitgemn dependent on amino acid

composition of the antigen-binding site Aa substitutions may alter the binding affinity of the antigens

Type I DM At least 17 other different genetic loci may

contribute susceptibility Polymorphisms in the promoter region of insulin

account for 10% of predisposition Genetic contributions not very strong component Most individuals with these haplotypes do not

develop diabetes Most individuals with type I DM do not have a first-

degree relative with the disorder

Type II DM Stronger genetic component Polygenic and multi-factorial Various genetic loci contribute to susceptibility Environmental factors further module phenotypic

expression Concordance in identical twins: 70-90% Genetic defect may not manifest itself unless and

environmental even or another genetic defect (obesity) is superimposed

Mutations account for only a small fraction of type II DM