Diabetes Mellitus: Causes and Mechanisms

Introduction

• Diabetes Mellitus is a condition where the body struggles to move glucose from the blood into cells.
• Results in high blood glucose levels with insufficient cellular glucose.
• Cells require glucose for energy, leading to cellular starvation despite the presence of glucose.

Hormonal Regulation of Blood Glucose

• Insulin and Glucagon are two key hormones controlling blood glucose levels.
• Insulin: Decreases blood glucose by facilitating cellular uptake of glucose.
  • Secreted by beta cells in the pancreas' islets of Langerhans.
• Glucagon: Increases blood glucose by promoting hepatic glucose production and glycogen breakdown.
  • Secreted by alpha cells in the pancreatic islets.

Types of Diabetes Mellitus

• Type 1 Diabetes Mellitus

  • Accounts for about 10% of diabetes cases.
  • Characterized by insufficient insulin production due to autoimmune destruction of pancreatic beta cells.
  • Involves a type 4 hypersensitivity response where T cells target beta cell antigens.
  • Genetic predisposition linked to HLA-DR3 and HLA-DR4 genes.
  • Symptoms include polyphagia, glycosuria, polyuria, and polydipsia.
  • Requires lifelong insulin therapy.

• Type 2 Diabetes Mellitus

  • Constitutes 90% of diabetes cases.
  • Involves insulin resistance and relative insulin deficiency.
  • Typically associated with lifestyle factors and genetic predisposition.

Pathophysiology of Type 1 Diabetes

• Genetic abnormality leads to loss of self-tolerance among T cells targeting beta cells.
• Destruction of beta cells reduces insulin, leading to high blood glucose.
• Symptoms arise after significant beta cell loss.

Complications: Diabetic Ketoacidosis (DKA)

• A serious complication predominantly in Type 1 Diabetes.
• Results from lipolysis and subsequent ketone body production by the liver.
• Increases blood acidity, causing symptoms like Kussmaul respiration.
• Potassium imbalances occur due to increased acidity and lack of insulin.
  • Leads to hyperkalemia and depletion of bodily potassium stores.

Review and Study Tools

• Various study resources and assessments are available for deeper understanding.
• Flashcards, USMLE Step 1 style questions, and pathology reviews are useful for exam preparation.

References

• Textbooks and journal articles provide foundational information (list includes Robbins Basic Pathology, Harrison's Principles of Internal Medicine, etc.).

This summary outlines the key points from the lecture on diabetes mellitus, focusing on its causes, hormonal regulation, types, pathophysiology, and complications. Use this as a study guide to reinforce understanding of diabetes and its management.