Homeostasis and Its Disruption

Introduction to Homeostasis

Homeostasis refers to the body's ability to maintain a stable internal environment despite changes in external conditions. This process is essential for optimal physiological function and survival.

• Definition: Homeostasis is the regulation of internal conditions such as temperature, pH, and glucose levels.

• Importance: Disruption of homeostasis can lead to disease and impaired bodily functions.

• Example: Diabetes mellitus is a key example of what happens when homeostasis of blood glucose regulation fails.

Diabetes Mellitus: Overview

Definition and Epidemiology

Diabetes mellitus is a metabolic disorder characterized by chronic hyperglycemia due to defective insulin secretion, insulin action, or both. It is a major public health concern affecting millions worldwide.

• Hyperglycemia: Elevated blood glucose levels are the hallmark of diabetes.

• Prevalence: Approximately 9% of Canadians have diabetes, with an additional 5-8 million having pre-diabetes.

• Economic Impact: Direct costs in Canada are estimated at $9-13 billion per year.

• Global Impact: Diabetes affects all organ systems and is associated with significant morbidity and mortality.

Types of Diabetes Mellitus

Classification

Diabetes mellitus is classified into several types based on etiology and pathophysiology.

• Type 1 Diabetes Mellitus (T1DM): Characterized by autoimmune destruction of pancreatic beta cells, resulting in absolute insulin deficiency.

• Type 2 Diabetes Mellitus (T2DM): Characterized by insulin resistance and relative insulin deficiency. Most common form, accounting for the majority of cases.

• Gestational Diabetes: Occurs during pregnancy; increases risk for T2DM later in life.

• Other Types: Includes secondary diabetes due to other diseases or medications.

Diagnostic Criteria for Diabetes Mellitus

Blood Glucose Measurements

Diagnosis of diabetes is based on specific blood glucose thresholds measured under fasting and postprandial conditions.

• Fasting Plasma Glucose (FPG): mmol/L ( mg/dL) indicates diabetes.

• Oral Glucose Tolerance Test (OGTT): mmol/L ( mg/dL) two hours after glucose load indicates diabetes.

• Impaired Glucose Tolerance: Fasting glucose between mmol/L ( mg/dL) is considered pre-diabetes.

Symptoms of Diabetes Mellitus

• Polyuria: Increased urine output due to osmotic diuresis.

• Polydipsia: Increased thirst due to fluid loss.

• Other Symptoms: Fatigue, blurred vision, and slow wound healing.

Prevalence and Demographics

Diabetes Prevalence by Age, Sex, and Ethnicity

Diabetes prevalence varies by demographic factors, including age, sex, and ethnicity.

Additional info: Prevalence is highest among American Indian adults in Arizona and lowest among White Americans.

Diabetes Insipidus vs. Diabetes Mellitus

Comparison

• Diabetes Insipidus: Characterized by excessive urine output and inability to concentrate urine, unrelated to blood glucose levels. The term 'insipidus' means 'without taste.'

• Diabetes Mellitus: Characterized by sweet-tasting urine due to high glucose content. The term 'mellitus' means 'sweet.'

• Key Difference: Diabetes insipidus is a disorder of water regulation, while diabetes mellitus is a disorder of glucose regulation.

Pathophysiology of Diabetes Mellitus

Mechanisms

Diabetes mellitus results from either insufficient insulin production or impaired insulin action, leading to chronic hyperglycemia and associated complications.

• Type 1: Autoimmune destruction of beta cells in the pancreas.

• Type 2: Insulin resistance in peripheral tissues and eventual beta cell dysfunction.

• Complications: Includes cardiovascular disease, kidney failure, neuropathy, and retinopathy.

Summary Table: Diagnostic Criteria for Diabetes Mellitus

Key Equations

• Fasting Plasma Glucose:

• Oral Glucose Tolerance Test (OGTT):

Conclusion

Diabetes mellitus exemplifies the consequences of disrupted homeostasis in human physiology. Understanding its types, diagnostic criteria, and epidemiology is essential for students of anatomy and physiology.