Lec 1 Notes - Glucose Intolerance

CONTROLLING BLOOD SUGAR

Insulin Regulation

• Insulin is the main regulator of blood sugar in the blood.

  • Produced by Beta Cells in the pancreas.

  • Function of Insulin: High levels drive sugar out of the blood into muscle, fat, and liver cells where it is stored.

  • Low levels allow sugar and other fuels to be released back into the blood.

• Basal Insulin: Overnight and between meals, levels of insulin in the bloodstream are low and constant, allowing the body to release sugar and other fuels from the liver.

• Normal Blood Sugar Levels: When you haven’t eaten, normal blood sugar levels are between 60-100 mg/dl.

• After eating, blood sugar levels peak at less than 140 mg/dl and then fall back to baseline. High levels of insulin help sugar out of the bloodstream.

Glucagon Regulation

• Glucagon controls the production of glucose and ketones.

  • Released overnight and between meals to help maintain blood sugar.

  • Signals the liver to breakdown starch or glycogen stores to form new glucose units and ketones.

  • Promotes breakdown of fat in fat cells.

  • Post-Meal Changes: Glucagon levels fall after a meal.

  • In diabetics, glucagon levels rise, causing blood sugar levels to increase after a meal.

Incretin Hormones

• Incretin hormones: Includes GLP-1 and GIP.

  • Released from the gut to signal beta cells to increase their insulin secretion and decrease alpha cells' release of glucagon.

  • GLP-1 Effects:

    • Slows down gastric emptying.

    • Acts on the brain to promote a feeling of fullness.

  • In diabetes: there is a sub-normal GIP, and beta cells fail to respond properly to GLP-1 which may explain why glucagon levels are not suppressed during a meal.

• Amylin: Released alongside insulin from beta cells with effects similar to GLP-1.

  • Decreases glucagon levels and slows food emptying, which further decreases the liver's glucose production during meals.

Stress and Gluco-Counter-Regulatory Hormones

• Stress Hormones: Epinephrine, cortisol, growth hormone, and glucagon are termed “stress” or “gluco-counter-regulatory” hormones, increasing blood sugar.

  • Epinephrine: Promotes sugar production and breakdown and the release of fat from the liver.

  • Cortisol: Makes fat and muscle cells resistant to the action of insulin and enhances glucose production by the liver, counterbalancing insulin.

    • Under stress or with synthetic cortisol (such as Prednisone), cortisol levels elevate, leading to insulin resistance.

  • Growth Hormone: Counterbalances insulin effects on muscle and fat, causing insulin resistance at high levels.

Type 1 Diabetes

Type 1 is essentially an "outside-in" trigger meeting a genetic predisposition.

• The Autoimmune Trigger (Type 1A): An environmental factor (like a virus) triggers the immune system in people with specific HLA genes. The body then mistakenly destroys its own pancreatic Beta cells.

• The "Honeymoon Phase": After the initial diagnosis, there may be a brief period where the remaining beta cells struggle to work one last time, making it seem like the diabetes is "gone." This is temporary.

• The Amylin Factor: You don't just lose insulin; you lose Amylin.

  • Role: Amylin is co-secreted with insulin to help manage glucose after you eat.

  • Result: Without it, post-meal glucose spikes are harder to control.

• Type 1B: This is the "idiopathic" version—same symptoms, but no evidence of autoimmunity or HLA links.

Type 2 Diabetes: The "Resistance"

Type 2 is a progressive failure of the body to use the insulin it makes.

1. The Path of Progression

It typically follows this sequence:

1. Insulin Resistance: Muscle and fat cells stop responding to insulin (Post-receptor defect).

2. Compensatory Hyperinsulinemia: The pancreas pumps out extra insulin to force the cells to listen.

3. Beta Cell Exhaustion: Eventually, the pancreas can't keep up. You end up with "inappropriately low" insulin levels for the amount of sugar in the blood.

2. Metabolic Syndrome (Dysmetabolic Syndrome)

Type 2 is rarely alone. It is usually part of a cluster of issues:

• Insulin Resistance & Hyperinsulinemia

• Obesity (Specifically "Central Adiposity" or belly fat)

• Hypertension (High blood pressure)

• Dyslipidemia (High cholesterol/triglycerides)

3. The "Toxicity" Cycle

• Glucose Toxicity & Lipotoxicity: High levels of sugar and fat in the blood actually poison the remaining beta cells, making them even less effective at secreting insulin.

PATHOPHYSIOLOGY GESTATIONAL DIABETES

Description

• Gestational Diabetes Mellitus (GDM): Any degree of glucose intolerance first recognized during pregnancy.

  • Insulin requirements increase during pregnancy due to:

    • Presence of insulin antagonists like human placental lactogen or chorionic somatomammotropin, and cortisol, which promote lipolysis and decrease glucose use.

    • Insulinase produced by the placenta.

PATHOPHYSIOLOGY OTHER CAUSES FOR GLUCOSE INTOLERANCE

Contributing Conditions

• Various genetic defects of the beta cell and insulin action, diseases of the exocrine pancreas, endocrinopathies, drugs, chemical agents, infections, immune disorders, and genetic syndromes can lead to variable degrees of glucose intolerance, including diabetes.

• Chronic Conditions: Liver and renal diseases can also result in glucose intolerance.

PATHOPHYSIOLOGY GLUCOSE INTOLERANCE

Gastrointestinal Role

• The gastrointestinal tract significantly influences glucose tolerance.

  • Upon food ingestion, incretin hormones (e.g., GLP-1 and GIP) are synthesized and secreted by specialized gut cells.

Incretin Hormones and Strategies

• The importance of incretin hormones has gained attention in developing new agents for improving glycemic control in patients with type 2 diabetes by:

  • Inhibiting dipeptidyl peptidase IV (DPP-4), the primary enzyme degrading incretin hormones in vivo.

  • Utilizing GLP-1 agonists.

Pathologic Defects

• Pathologic defects observed in type 2 diabetes mellitus and sometimes in impaired glucose tolerance include:

  • Postprandial Hyperglucagonemia: Elevated glucagon levels following meals.

  • Dysregulation of Gastric Emptying: Changes in the speed at which food exits the stomach.

  • Loss of Incretin Effect: Diminished efficacy of incretin hormones in regulating glucose.

FREQUENCY OF GLUCOSE INTOLERANCE

Prevalence and Statistics

• Type 2 diabetes: The predominant form of clinical diabetes, constituting 90-95% of cases. Most commonly occurs in middle age and is reaching epidemic proportions.

• Gestational diabetes: Develops in approximately 4% of pregnancies in the United States.

FREQUENCY OF GLUCOSE INTOLERANCE (Continued)

Global Statistics

• Worldwide Rates:

  • Lowest diabetes prevalence (<1%) in certain African and Chinese populations, as well as rural Mapuche Indians in Chile.

  • Highest rates of type 2 diabetes observed in the Pima Indians of Arizona (50%) and the Nauruan people (35%) of the Pacific island of Nauru.

MORTALITY/MORBIDITY

Impact of Diabetes

• Diabetes: The seventh leading cause of death in the United States. It contributes to numerous deaths by other causes such as cardiovascular disease (CVD).

  • Overall, the death rate among people with diabetes is approximately twice that of individuals of similar age without diabetes, attributed to:

    • Acute metabolic complications

    • Leading cause of end-stage renal disease

    • Leading cause of blindness

    • Increased risk for heart disease and stroke

    • Higher risk for neuropathy and gangrene.

Gestational Diabetes Effects

• Gestational Diabetes Mellitus (GDM):

  • Increased risk for fetal and neonatal morbidity and mortality, as well as obstetric complications.

  • Higher risk of shoulder dystocia due to macrosomia (larger babies).

  • Increased maternal risk for glucose intolerance and type 2 diabetes.

  • Heightened incidence of obesity in children born to mothers with GDM.

Prediabetes Risks

• Prediabetes: A significant risk factor for diabetes, with about 50% of individuals with prediabetes progressing to diabetes within 10 years.

  • Baseline plasma glucose is the most consistent predictor of progression.

  • Increased risk of macrovascular complications (e.g., coronary artery disease, gangrene, stroke) prior to developing type 2 diabetes (T2DM).

RACE & ETHNICITY

Risk Factors by Population

• Native Americans and certain Pacific island populations exhibit the highest risk for glucose intolerance.

• Higher rates of glucose intolerance among African Americans and Hispanics compared to non-Hispanic whites.

• Type 2 diabetes prevalence is more common in ethnic minorities, while type 1 diabetes occurs more frequently in whites, particularly those of Northern European descent.

  • Type 1B diabetes is more common in individuals of Asian or African descent.

SEX

Gender Differences

• According to WHO global data, the prevalence ratio of diabetes between men and women varies significantly, with no consistent trend.

  • Impaired glucose tolerance is, however, more common in women than in men.

  • The difference in frequency between sexes likely relates to underlying factors like pregnancy and obesity rather than a sex-specific genetic tendency.

AGE

Age Trends in Diabetes

• Type 1 Diabetes: Most commonly presents in children and adolescents but can occur at any age.

• Type 2 Diabetes: Usually begins in middle life or later, typically after age 30. Its prevalence increases with age.

  • A growing incidence of type 2 diabetes in childhood and adolescence correlates with increasing obesity rates.

CLINICAL PRESENTATION - HISTORY

Symptoms in Type 1 Diabetes

• Warning symptoms of type 1 diabetes include:

  • Polyuria, Polydipsia, and Polyphagia due to hyperglycemia.

  • Patients may experience unexplained weight loss and easy fatigue.

  • Severe Symptoms: Irritability, drowsiness, and loss of consciousness may occur, particularly as ketoacidosis develops.

    • Progression leads to dehydration, electrolyte abnormalities, osmolality, and acid-base disturbances.

  • After ketoacidosis presentation, a patient may revert to normoglycemia without therapy, known as the honeymoon phase.

Symptoms in Type 2 Diabetes

• Patients with type 2 diabetes may have similar symptoms as type 1 diabetes but are often asymptomatic.

  • Hyperosmolar Nonketotic Coma: Characterized by severe dehydration due to osmotic diuresis from hyperglycemia. Ketoacidosis, although rare, may also occur in type 2 diabetes.

  • History: Includes frequent infections, poor wound healing, blurred vision, and numbness or tingling sensations in extremities.

Prediabetes Symptoms

• Categories of IGT and impaired fasting glucose are considered prediabetes due to their role as risk factors for future diabetes and cardiovascular disease.

  • Patients with impaired glucose homeostasis are generally asymptomatic.

  • Cardiovascular disease risk factors may also be present, along with associated history of hypertension, obesity, dyslipidemia, or macrovascular disease.

CLINICAL PRESENTATION - PE

Acute Presentation (Diabetic Ketoacidosis)

• Overt hyperglycemia that progresses to diabetes results in signs of dehydration.

  • Symptoms include hypotension and signs of hemodynamic decompensation with worsening hyperglycemia.

  • Metabolic Deterioration: Kussmaul respiration and altered consciousness due to metabolic derangement are common in acute worsening.

  • Evaluation for precipitating factors like fever from infectious processes is essential.

Routine Evaluation

• Measurements for routine evaluation:

  • Weight, height, waist, and hip measurements determine BMI, risk level, and presence of truncal obesity.

    • Up to 90% of type 2 diabetes patients are obese.

    • Central adiposity can occur even with a normal BMI.

  • Peripheral signs of lipid abnormalities and atherosclerosis may present as premature arcus cornealis, xanthelasma, eruptive xanthomata, and tendon xanthomata.

Blood Pressure Importance

• Blood Pressure Measurement: Critical component as hypertension is frequent in dysmetabolic syndrome.

  • Hypertension occurs 1.5-2 times more often in individuals with diabetes than in those without.

  • About 40% of individuals with hypertension may also have impaired glucose tolerance.

Eye and Neurologic Examination

• Eye Examination: Look for pupillary abnormalities, cataracts, refractive errors, and retinopathy due to chronic uncontrolled hyperglycemia.

• Neurologic Examination: Assess for muscle wasting, sensory abnormalities, and diabetic neuropathy characteristics.

Clinical Features in Genetic Syndromes

• Specific phenotypic characteristics found in genetic syndromes include:

  • Type A Insulin Resistance: Patients may exhibit acanthosis nigricans (hyperpigmentation and skin thickening of flexural areas) and features of hyperandrogenism.

DERM ALERT

Common Diabetic Skin Conditions

• Diabetic Dermopathy (Shin Spots): Most common finding in diabetes, characterized by round/oval atrophic hyperpigmented macules on the pretibial areas bilaterally.

• Xanthoma Eruptiva: Pink papules with “creamy” center due to elevated triglycerides, commonly seen on extensor surfaces and popliteal region in diabetes patients.

• Necrobiosis Lipodica Diabeticorum: Degenerative collagen disease presenting as atrophic, waxy plaques, often ulcerative and typically found in the pretibial region, accompanied by fluid-filled bullae in hands/feet due to peripheral neuropathy.

Diabetic Ulcers and Other Skin Conditions

• Diabetic Ulcers: Ulcerations in feet or lower legs due to loss of sensation (peripheral neuropathy) or ischemic changes due to arteriosclerosis.

• Candidiasis: Recurrent yeast infections may signify elevated glucose levels.

• Kyrle’s Disease (Reacting Perforating Collagenosis): Pruritic papules with keratotic plugs, usually on legs but can affect face and arms; commonly associated with kidney disease.

CAUSES OF GLUCOSE INTOLERANCE

Genetic and Structural Defects

• Genetic Defects:

  • MODY Types:

    • Mutation on chromosome 12 (HNF-1 alpha - MODY3).

    • Mutation on chromosome 7p (glucokinase gene - MODY2).

    • Mutation on chromosome 20 (HNF-4 alpha - MODY1).

• Insulin Action Defects: Structural/function anomalies of insulin receptor or post-receptor signal transduction pathways.

  • Includes Type A insulin resistance and Leprechaunism.

Exocrine Pancreas Diseases

• Conditions affecting the exocrine pancreas include:

  • Pancreatitis

  • Trauma

  • Infection

  • Pancreatectomy

  • Pancreatic cancer

  • Cystic fibrosis

  • Hemochromatosis

Endocrine Diseases and Drugs

• Endocrine Diseases: Excess production of insulin antagonists, e.g.,

  • Acromegaly

  • Cushing syndrome

  • Glucagonoma

  • Pheochromocytoma

  • Hyperthyroidism

• Drugs/Chemicals: Adverse effects from

  • Thiazides

  • Glucocorticoids

  • Oral contraceptives

  • Beta-adrenergic agonists

  • Nicotinic acid

  • Thyroid hormone

Infectious and Immune Causes

• Infections: Associated with beta-cell destruction, including:

  • Rubella

  • Coxsackievirus B

  • Mumps

  • Cytomegalovirus

  • Adenovirus

• Immune-Mediated Causes: Anti-insulin receptor abnormalities.

Genetic Syndromes and Pregnancy

• Genetic Syndromes: Examples include Down syndrome, Klinefelter syndrome, Turner syndrome.

• Pregnancy: Gestational diabetes mellitus; the risk of diabetes increases with parity.

Obesity and Other Factors

• Obesity: A powerful determinant of glucose intolerance, resulting from genetic interactions and acquired factors like physical inactivity and dietary habits.

• Other Causes: Liver disease (cirrhosis) and renal failure can also lead to glucose intolerance.

LABORATORY STUDIES

Screening Tests

• Plasma Glucose Measurement: Used as a screening test; fasting plasma glucose studies preferred diagnostic test per ADA.

  • Random plasma glucose measurement is acceptable in the presence of classic diabetes symptoms.

Oral Glucose Tolerance Test (OGTT)

• OGTT: Standard oral glucose tolerance test measures plasma glucose concentration two hours after a 75-g oral glucose load.

  • Seldom used as confirmatory for diabetes diagnosis but helpful when fasting or random results are inconclusive.

HBA1C

Measurement for Diagnosis

• In 2010, ADA approved HbA1C as a diagnostic tool:

  • Greater than 6.5% indicates diabetes.

  • 5.6-6.4% categorized as pre-diabetes.

• Serves as an index of hyperglycemia severity over the preceding 6 to 8 weeks, indicating chronic hyperglycemia and predicting chronic complications.

ADA DIAGNOSTIC CRITERIA

Normal Glucose Homeostasis

• Criteria:

  • HbA1C: less than 5.6%

  • Fasting plasma glucose: less than 100 mg/dL

  • 2-hour OGTT: less than 140 mg/dL after 75-g oral glucose load.

Prediabetes

• Prediabetes Criteria:

  • HbA1C: 5.6 to 6.4%

  • Fasting plasma glucose: 100 to 125 mg/dL.

  • Cut point for impaired fasting glucose has been reduced from 110 mg/dL to capture more at-risk individuals.

  • 2-hour OGTT result of 140-199 mg/dL.

Diabetes Mellitus

• Diabetes Criteria:

  • HbA1C: 6.5% or higher.

  • Fasting plasma glucose: 126 mg/dL or higher.

  • Random plasma glucose level: 200 mg/dL or higher accompanied by classic hyperglycemic symptoms.

  • 2-hour OGTT: 200 mg/dL or higher after a 75-g oral glucose load.

SCREENING FOR DIABETES

Recommended Protocol

• Screening for type 2 diabetes should occur every three years in all individuals older than 45 years. Normal results necessitate repeated testing every three years, with more frequent assessments based on risk status.

Risk Factors for Earlier Testing

• Testing is indicated at younger ages or more frequently for individuals who are overweight (BMI >= 25) with additional risk factors:

  • Habitual physical inactivity

  • First-degree relative with diabetes

  • High-risk ethnic background (Hispanic, American Indian, Asian American, African American, Pacific Islander)

  • History of delivering a baby that was large for gestational age or a history of GDM.

  • Hypertension (blood pressure ≥ 140/90 mm Hg)

  • Low HDL cholesterol (< 35 mg/dL) or high triglycerides (≥ 250 mg/dL)

  • Polycystic ovary syndrome (PCOS) or conditions associated with insulin resistance.

Screening in Children

• Type 2 diabetes screening in children:

  • Overweight (>85th percentile for age & sex) + 2 risk factors:

    • Family history of T2DM

    • High-risk race/ethnicity

    • Signs of insulin resistance

    • Maternal history of diabetes or GDM during gestation.

  • Start screening at age 10 or at puberty, then every 3 years.

Gestational Diabetes Protocol

• Perform a 75-g OGTT at:

  • Fasting, 1 hour, and 2-hour intervals after an 8-hour fast during 24-28 weeks of gestation.

  • Screen at the first prenatal visit for high-risk women using standard criteria (fasting plasma glucose, HbA1C).

  • Women with GDM should be screened for persistent diabetes 6-12 weeks postpartum and undergo routine screening every three years thereafter.

OTHER LABORATORY STUDIES

Tests and Indicators

• Urinalysis: Important for detecting ketonuria and glycosuria indicative of acute decompensation. Significant proteinuria may indicate diabetic nephropathy. Urine microalbumin serves as an early marker for renal impairment and endothelial dysfunction.

OTHER LABORATORY STUDIES (Continued)

Electrolyte and Renal Function Evaluation

• Serum electrolytes, BUN, creatinine, uric acid, and blood gas analysis are essential during acute decompensation, as metabolic derangements due to fluid and electrolyte loss are common.

Assessments before Treatment

• Ensure normal renal and hepatic function before initiating certain oral antidiabetic agents.

  • Liver function tests exclude hepatic disease prior to commencing drugs like biguanides and thiazolidinediones (TZDs).

  • Periodic assessments are necessary during TZD treatment.

Lipid Profile and CBC

• Lipid Profile: May show increased triglycerides, reflecting poor glycemic control, often normalizing with euglycemia. Other abnormalities might include high total cholesterol and LDL levels.

• CBC: An increased white blood cell count may indicate acute infection; ketoacidosis can lead to leukocytosis.

TREATMENT

Routine Management

• Routine evaluation and treatment in an ambulatory setting are feasible for the majority of patients.

  • Patients with acute decompensation may require inpatient care.

  • The core goal of glucose intolerance management is glycemic control.

Lifestyle Modifications

• Intensive lifestyle modifications effectively delay or prevent diabetes cost-effectively. Non-pharmacologic approaches include:

  • Diet

  • Exercise

  • Counseling for smoking cessation and alcohol use.

  • Adjusting medication that adversely affects glucose tolerance (substituting agents or reducing dosages).

Dietary Recommendations

• Medical Nutrition Therapy: Guided by ADA recommendations, individualized per patient needs, considering weight, height, physical activity levels, and nutrient requirements.

  • Aim for a moderate weight loss of at least 7% of body weight.

  • Suggested diets include low carbohydrate, low fat, calories-restricted, or a Mediterranean diet.

  • Limit alcohol intake (1 drink/day for women, 2 drinks/day for men).

Physical Activity Guidelines

• Promote a high level of physical activity adapted to patient capabilities and health status.

  • Most patients benefit from tailored exercise programs, encouraged to achieve a minimum of 150 minutes of moderate exercise weekly.

Medication for Type 1 and Type 2 Diabetes

• All patients with type 1 diabetes are insulin-dependent.

• Type 2 diabetes can be treated effectively with oral or injectable medications, with or without added insulin.

  • The natural history of type 2 diabetes involves progressive beta-cell deterioration, leading to secondary failure of oral agents and the eventual need for insulin therapy.

• Gestational diabetes is treated with insulin and/or lifestyle adjustments. Oral agents are not recommended during pregnancy.

Prediabetes Management

• Current management for prediabetes focuses on aggressive lifestyle modifications.

  • The Diabetes Prevention Program (DPP) demonstrated metformin therapy and intensive lifestyle intervention reduce diabetes risk by 31% and 58%, respectively, compared to placebo.

Bariatric Surgery Benefits

• Bariatric Surgery: Recommended for patients with a BMI above 35.

  • Leads to weight loss and improved glycemic control, resulting in nearly complete normalization of glycemic control in 40-95% of type 2 diabetes patients.

    • Meta-analysis indicated 78% had sustained diabetes remission at two-year follow-up.

Pharmacological Therapy Indications

• Consider pharmacologic therapy in patients with:

  • Fasting glucose > 126 mg/dL

  • Postprandial glucose (OGTT) > 160 mg/dL

  • HbA1C > 7%.

FOLLOW UP

Monitoring Parameters

• Regular monitoring for:

  • Medication compliance and adverse effects.

  • Blood glucose and HbA1C levels.

  • Dietary consultation and exercise prescriptions.

  • Referrals to endocrinologists, dietitians, cardiologists, ophthalmologists, nephrologists as necessary.

Patient Instructions

• Maintain a healthy diet and increase physical activity as tolerated.

• Encourage quitting smoking and avoiding alcohol abuse. Celebrate achieved A1C levels appropriately, noting the irony of indulgences like cupcakes amid healthy goals.

COMPLICATIONS OF GLUCOSE INTOLERANCE

Macrovascular and Microvascular Disease

• Complications arising from prediabetes and diabetes are classified as:

  • Macrovascular Disease: Includes coronary artery disease, peripheral vascular disease, and stroke.

  • Microvascular Disease: Encompasses nephropathy, retinopathy, neuropathy, and acute metabolic complications.

PROGNOSIS

Long-term Risk Dynamics

• Prediabetes poses a heightened risk for type 2 diabetes, with up to 50% progressing within 10 years:

  • One-third may revert to normal glucose tolerance, while others may persist with IGT, assessed via OGTT.

• For Gestational Diabetes Mellitus (GDM):

  • Glucose tolerance is typically normal after delivery, yet there remains a significant lifetime risk for IGT and diabetes.

PATIENT EDUCATION

Teaching and Support

• Diabetic Nurse Educator Referral: Many clinics have dedicated staff for patient education.

• Education should encompass disease knowledge, treatment plans, self-monitoring, potential complications, and preventive measures, including family member involvement in hypoglycemia management.