12 Diabetes Mellitus

Diabetes mellitus is a group of metabolic disorders characterized by chronic hyperglycemia (high blood sugar) resulting from defects in insulin secretion, insulin action, or both. Diabetes is a leading cause of morbidity and mortality worldwide, and its complications can affect multiple organ systems.

1. Pathophysiology
   
   • Insulin and Glucose Metabolism: Insulin, a hormone produced by the pancreas, plays a key role in glucose metabolism. It facilitates the uptake of glucose by cells for energy production and storage as glycogen. In diabetes, insulin production is insufficient (Type 1 diabetes) or the body’s cells are resistant to insulin’s effects (Type 2 diabetes), leading to elevated blood glucose levels.
   • Types of Diabetes:
     • Type 1 Diabetes: An autoimmune condition where the immune system attacks and destroys insulin-producing beta cells in the pancreas, leading to an absolute deficiency of insulin. It typically presents in childhood or adolescence.
     • Type 2 Diabetes: Characterized by insulin resistance and relative insulin deficiency. It is more common in adults and is strongly associated with obesity, physical inactivity, and genetic factors.
     • Gestational Diabetes: A form of diabetes that occurs during pregnancy and typically resolves after delivery, though it increases the risk of developing Type 2 diabetes later in life.
2. Clinical Manifestations
   
   • Hyperglycemia: Persistent high blood sugar levels are the hallmark of diabetes and may cause symptoms such as excessive thirst (polydipsia), frequent urination (polyuria), and increased hunger (polyphagia).
   • Fatigue and Weakness: Due to the body’s inability to use glucose efficiently for energy.
   • Blurred Vision: Resulting from osmotic changes in the lens of the eye due to high blood glucose levels.
   • Weight Loss: Particularly in Type 1 diabetes, where the body breaks down fat and muscle for energy due to the lack of insulin.
3. Diagnosis
   
   • The diagnosis of diabetes is primarily based on laboratory tests that measure blood glucose levels. Several tests are available, each with specific criteria for diagnosing diabetes.
   • Fasting Plasma Glucose (FPG) Test
     • Description: The FPG test measures blood glucose levels after an individual has fasted for at least 8 hours.
     • Diagnostic Criteria:
       • • Normal: FPG < 100 mg/dL (5.6 mmol/L)
         • Prediabetes: FPG 100–125 mg/dL (5.6–6.9 mmol/L)
         • Diabetes: FPG ≥ 126 mg/dL (7.0 mmol/L) on two separate occasions
     • Clinical Significance: The FPG test is a simple and widely used screening tool for diabetes. Elevated fasting glucose levels indicate impaired insulin function and the presence of hyperglycemia, a hallmark of diabetes.
   • Oral Glucose Tolerance Test (OGTT)
     • Description: The OGTT measures blood glucose levels before and 2 hours after the ingestion of a 75-gram glucose solution.
       • Diagnostic Criteria:
         • Normal: 2-hour plasma glucose < 140 mg/dL (7.8 mmol/L)
         • Prediabetes: 2-hour plasma glucose 140–199 mg/dL (7.8–11.0 mmol/L)
         • Diabetes: 2-hour plasma glucose ≥ 200 mg/dL (11.1 mmol/L)
     • Clinical Significance: The OGTT is particularly useful in diagnosing gestational diabetes and assessing glucose tolerance in individuals with impaired fasting glucose (IFG). It provides a more comprehensive assessment of the body’s ability to handle glucose.
   • Glycated Hemoglobin (HbA1c) Test
     • Description: The HbA1c test measures the percentage of hemoglobin that is glycated (bound to glucose) over the past 2 to 3 months.
     • Diagnostic Criteria:
       • Normal: HbA1c < 5.7%
       • Prediabetes: HbA1c 5.7%–6.4%
       • Diabetes: HbA1c ≥ 6.5% on two separate occasions
     • Clinical Significance: The HbA1c test provides an overview of long-term blood glucose control and is a key diagnostic and monitoring tool in diabetes management. It reflects average blood glucose levels over a period, offering insight into the effectiveness of treatment strategies.
   • Random Plasma Glucose Test
     • Description: This test measures blood glucose levels at any time of the day, regardless of fasting status.
     • Diagnostic Criteria:
       • Diabetes: Random plasma glucose ≥ 200 mg/dL (11.1 mmol/L) with symptoms of hyperglycemia (e.g., polyuria, polydipsia, unexplained weight loss)
     • Clinical Significance: The random plasma glucose test is often used in the presence of classic diabetes symptoms to confirm a diagnosis quickly, especially in emergency settings.
   • Monitoring Glycemic Control
     • Once diabetes is diagnosed, ongoing monitoring of blood glucose levels is essential to assess the effectiveness of treatment and prevent complications. Several tests are commonly used for this purpose.
   • Self-Monitoring of Blood Glucose (SMBG)
     • Description: SMBG involves patients using a glucometer to measure their blood glucose levels at various times throughout the day.
     • Clinical Significance: SMBG is crucial for patients on insulin therapy, providing immediate feedback on blood glucose levels and allowing for real-time adjustments in insulin dosing, diet, and physical activity. It helps in preventing both hyperglycemia and hypoglycemia.
   • Continuous Glucose Monitoring (CGM)
     • Description: CGM systems use a sensor placed under the skin to continuously measure glucose levels in interstitial fluid, providing real-time glucose readings every few minutes.
     • Clinical Significance: CGM offers a more comprehensive picture of glucose trends throughout the day and night, identifying patterns and fluctuations that may not be captured by SMBG alone. CGM is particularly useful for patients with Type 1 diabetes and those experiencing frequent hypoglycemia.
4. Management of Diabetes Mellitus
   • Lifestyle Modifications: Diet and exercise are foundational to diabetes management. Patients are advised to follow a balanced diet with controlled carbohydrate intake and engage in regular physical activity.
   • Pharmacological Treatment:
     • Insulin Therapy: Essential for patients with Type 1 diabetes and some patients with advanced Type 2 diabetes.
     • Oral Hypoglycemic Agents: Such as metformin, sulfonylureas, and DPP-4 inhibitors, are used to manage blood glucose levels in Type 2 diabetes.
     • Continuous Glucose Monitoring (CGM): Technology that provides real-time data on blood glucose levels, allowing for more precise management.
   • Patient Education: Nurses play a critical role in educating patients about blood glucose monitoring, medication adherence, recognizing signs of hypo- and hyperglycemia, and the importance of regular follow-up.
5. Complications of Diabetes Mellitus
   • Acute Complications: Include diabetic ketoacidosis (DKA) in Type 1 diabetes, characterized by severe hyperglycemia, ketonemia, and metabolic acidosis, and hyperosmolar hyperglycemic state (HHS) in Type 2 diabetes, marked by extreme hyperglycemia without significant ketosis.
   • Chronic Complications: Long-term complications of poorly managed diabetes include cardiovascular disease, neuropathy, nephropathy, retinopathy, and increased susceptibility to infections.

 Assessing and Monitoring Complications

Diabetes can lead to various complications, including cardiovascular disease, nephropathy, retinopathy, and neuropathy. Laboratory and diagnostic tests are essential for the early detection and monitoring of these complications.

• Lipid Profile
  • Description: The lipid profile measures total cholesterol, low-density lipoprotein (LDL), high-density lipoprotein (HDL), and triglycerides.
  • Clinical Significance: Diabetes is associated with an increased risk of cardiovascular disease. Regular monitoring of lipid levels is important for managing this risk. LDL is typically targeted for reduction to prevent atherosclerosis, while HDL and triglycerides are also important markers of cardiovascular health.
• Urine Albumin-to-Creatinine Ratio (UACR)
  • Description: The UACR test measures the amount of albumin in the urine, relative to creatinine, to assess kidney function.
  • Clinical Significance: Microalbuminuria (30–299 mg/g creatinine) is an early indicator of diabetic nephropathy. Regular UACR testing helps in detecting kidney damage at an early stage, allowing for timely interventions to prevent progression to end-stage renal disease (ESRD).
• Serum Creatinine and Estimated Glomerular Filtration Rate (eGFR)
  • Description: Serum creatinine is used to estimate glomerular filtration rate (eGFR), a measure of kidney function.
  • Clinical Significance: Monitoring eGFR provides insight into the severity of kidney impairment. A declining eGFR may indicate the progression of diabetic nephropathy, necessitating adjustments in treatment to protect kidney function.
• Retinal Examination
  • Description: Regular retinal examinations, often performed using fundus photography or optical coherence tomography (OCT), are essential for detecting diabetic retinopathy.
  • Clinical Significance: Diabetic retinopathy is a leading cause of blindness in adults. Early detection through regular eye exams allows for timely interventions, such as laser therapy or intravitreal injections, to prevent vision loss.
• Nerve Conduction Studies (NCS) and Electromyography (EMG)
  • Description: NCS and EMG are used to assess nerve function and detect peripheral neuropathy.
  • Clinical Significance: Diabetic neuropathy can lead to significant morbidity, including pain, loss of sensation, and an increased risk of foot ulcers. Nerve conduction studies help in diagnosing neuropathy early, allowing for interventions to manage symptoms and prevent complications.

Advanced Diagnostic Techniques

• In addition to standard laboratory tests, advanced diagnostic techniques are increasingly being used to assess and manage diabetes and its complications.
• Insulin and C-Peptide Levels
  • Description: Measuring insulin and C-peptide levels helps differentiate between Type 1 and Type 2 diabetes and assess beta-cell function.
  • Clinical Significance: Low insulin and C-peptide levels are indicative of Type 1 diabetes, while elevated levels suggest insulin resistance, as seen in Type 2 diabetes. These tests can guide treatment decisions, particularly in atypical cases.
• Genetic Testing
  • Description: Genetic testing can identify specific mutations associated with monogenic forms of diabetes, such as MODY (Maturity-Onset Diabetes of the Young).
  • Clinical Significance: Identifying the genetic basis of diabetes can lead to personalized treatment approaches and a better understanding of disease risk in family members.
• Advanced Imaging Techniques
  • Description: Techniques such as coronary artery calcium (CAC) scoring, cardiac MRI, and Doppler ultrasound are used to assess cardiovascular risk and complications in diabetic patients.
  • Clinical Significance: Diabetes significantly increases the risk of cardiovascular disease. Advanced imaging techniques provide detailed information on cardiovascular health, allowing for more targeted and effective interventions.