Type 1 and Type 2 Diabetes Mellitus: Diagnosis, Management, and Complications for PLAB 1
This module covers the essential knowledge required for the PLAB 1 exam regarding Type 1 and Type 2 Diabetes Mellitus, focusing on diagnosis, management strategies, and common complications, aligned with UK guidelines.
Understanding Diabetes Mellitus
Diabetes Mellitus (DM) is a chronic metabolic disorder characterized by elevated blood glucose levels (hyperglycemia). This occurs due to defects in insulin secretion, insulin action, or both. Understanding the fundamental differences between Type 1 and Type 2 DM is crucial for effective diagnosis and management.
Type 1 Diabetes Mellitus (T1DM)
T1DM is an autoimmune condition where the body's immune system mistakenly attacks and destroys the insulin-producing beta cells in the pancreas. This leads to an absolute deficiency of insulin. It typically presents in childhood or adolescence but can occur at any age.
Type 2 Diabetes Mellitus (T2DM)
T2DM is characterized by a combination of insulin resistance (where the body's cells don't respond effectively to insulin) and a relative deficiency in insulin secretion. It is strongly associated with obesity, physical inactivity, and genetic factors. It typically develops gradually in adulthood but is increasingly seen in younger individuals.
Diagnosis of Diabetes Mellitus
| Diagnostic Criteria | Fasting Plasma Glucose (FPG) | 2-Hour Plasma Glucose (OGTT) | HbA1c | Random Plasma Glucose |
|---|---|---|---|---|
| Diabetes Mellitus | ≥ 7.0 mmol/L (126 mg/dL) | ≥ 11.1 mmol/L (200 mg/dL) | ≥ 48 mmol/mol (≥ 6.5%) | ≥ 11.1 mmol/L (200 mg/dL) with classic symptoms |
| Impaired Fasting Glucose (IFG) | 5.6–6.9 mmol/L (100–125 mg/dL) | N/A | N/A | N/A |
| Impaired Glucose Tolerance (IGT) | N/A | 7.8–11.0 mmol/L (140–199 mg/dL) | N/A | N/A |
Diagnosis can be made with any one of the first three criteria on two separate occasions. If a random plasma glucose is elevated with classic symptoms of hyperglycemia, a single test is sufficient. For T1DM, autoantibody testing (e.g., anti-GAD) can support the diagnosis, especially in atypical presentations.
Management of Diabetes Mellitus
General Principles
Management is individualized and aims to achieve optimal glycemic control, prevent complications, and improve quality of life. Key components include lifestyle modification (diet and exercise), pharmacological therapy, and regular monitoring.
Type 1 Diabetes Mellitus Management
The cornerstone of T1DM management is lifelong insulin replacement therapy. This typically involves a basal-bolus regimen using multiple daily injections (MDI) or continuous subcutaneous insulin infusion (CSII) via an insulin pump. Carbohydrate counting and regular blood glucose monitoring are essential.
Insulin therapy for T1DM aims to mimic the physiological pattern of insulin secretion. Basal insulin provides a steady background level, while bolus insulin is administered before meals to cover carbohydrate intake and correct hyperglycemia. Different types of insulin (rapid-acting, short-acting, intermediate-acting, long-acting) are used to achieve this. The goal is to maintain blood glucose levels within a target range (e.g., 4-7 mmol/L before meals, < 8.5 mmol/L 2 hours after meals) and an HbA1c of ≤ 48 mmol/mol (≤ 6.5%).
Text-based content
Library pages focus on text content
Type 2 Diabetes Mellitus Management
Management of T2DM starts with lifestyle modifications: a healthy diet, regular physical activity, and weight loss if overweight or obese. If glycemic targets are not met, pharmacological therapy is introduced. The first-line oral antidiabetic drug is typically metformin. Other classes of oral agents and injectable non-insulin therapies (e.g., GLP-1 receptor agonists) may be used sequentially or in combination, depending on individual needs, comorbidities, and drug efficacy/tolerability. Insulin therapy may be required in later stages of the disease.
| Drug Class | Mechanism of Action | Key Considerations |
|---|---|---|
| Metformin | Reduces hepatic glucose production, increases insulin sensitivity | First-line; GI side effects common; contraindicated in renal impairment (eGFR < 30) |
| Sulfonylureas | Stimulate insulin secretion | Risk of hypoglycemia, weight gain |
| DPP-4 Inhibitors | Increase incretin levels, enhancing insulin secretion and reducing glucagon | Weight neutral, low risk of hypoglycemia |
| SGLT2 Inhibitors | Inhibit glucose reabsorption in the kidneys, increasing urinary glucose excretion | Risk of UTIs, genital infections; beneficial for cardiovascular and renal outcomes |
| GLP-1 Receptor Agonists | Mimic incretin effect, promoting insulin secretion, suppressing glucagon, slowing gastric emptying | Weight loss, cardiovascular benefits; injectable; GI side effects common |
Complications of Diabetes Mellitus
Diabetes can lead to both acute and chronic complications. Effective management aims to prevent or delay these.
Acute Complications
Diabetic Ketoacidosis (DKA): Primarily seen in T1DM, characterized by hyperglycemia, ketosis, and metabolic acidosis. Presents with polyuria, polydipsia, nausea, vomiting, abdominal pain, and Kussmaul breathing. Requires urgent hospital admission and intravenous fluid resuscitation, insulin therapy, and electrolyte correction. Hyperosmolar Hyperglycemic State (HHS): More common in T2DM, characterized by severe hyperglycemia, profound dehydration, and hyperosmolarity, with minimal or no ketosis. Presents with extreme thirst, polyuria, confusion, and neurological deficits. Management involves aggressive fluid replacement and insulin therapy.
Chronic Complications
These arise from prolonged hyperglycemia and affect various organ systems. Microvascular Complications:
- Diabetic Retinopathy: Damage to blood vessels in the retina, leading to vision loss. Screening is essential.
- Diabetic Nephropathy: Damage to the kidneys, potentially leading to end-stage renal disease. Regular monitoring of albuminuria and renal function is crucial.
- Diabetic Neuropathy: Nerve damage, commonly affecting the peripheral nerves (sensory, motor, autonomic). Can manifest as pain, numbness, tingling, and gastrointestinal or cardiovascular dysfunction. Macrovascular Complications:
- Cardiovascular Disease: Increased risk of coronary artery disease, myocardial infarction, stroke, and peripheral arterial disease. Management includes blood pressure control, lipid management, and antiplatelet therapy. Other Complications:
- Diabetic Foot Ulcers: Due to neuropathy and peripheral arterial disease, leading to increased risk of infection and amputation. Regular foot care and examination are vital.
Remember: The UK's National Institute for Health and Care Excellence (NICE) provides comprehensive guidelines for the diagnosis and management of diabetes, which are essential for PLAB preparation.
Insulin resistance and a relative deficiency in insulin secretion.
Diabetic Ketoacidosis (DKA).
Metformin.
Learning Resources
Provides comprehensive guidance on the diagnosis and management of Type 1 diabetes in children and young people, relevant for understanding the condition's progression and treatment principles.
Details the management of Type 2 diabetes in adults, covering diagnosis, lifestyle, pharmacological interventions, and complication prevention, crucial for PLAB preparation.
An authoritative overview of diabetes, its types, causes, and symptoms, offering a good foundational understanding for learners.
Provides accessible information on diabetes, including symptoms, causes, diagnosis, and treatment options, aligned with UK healthcare practices.
An educational module from BMJ Learning offering in-depth knowledge on Type 1 diabetes, suitable for enhancing clinical understanding.
A comprehensive tutorial on Type 2 diabetes mellitus, covering its pathophysiology, diagnosis, and management strategies.
Offers detailed clinical information on diabetes mellitus, including diagnostic criteria, management pathways, and complications, from a UK perspective.
A detailed clinical overview of T1DM management, providing in-depth information on insulin therapy, monitoring, and complication management.
An in-depth resource on the medical management of T2DM, covering pharmacological agents, lifestyle interventions, and treatment goals.
Access to reports from the National Diabetes Audit, providing insights into current diabetes care standards and outcomes in the UK.