Diabetes Mellitus and Insulin Hormone Overview

Study Notes

Definition: A chronic condition characterized by elevated blood sugar levels due to insufficient insulin production or resistance.
Etymology: "Honey urine" from ancient Greek, referring to the sweet-tasting urine of individuals with the condition.
Insulin Deficiency: Can be absolute, where the pancreas does not produce insulin, or relative, where the body does not effectively use the insulin it produces.
Metabolic Impact: Affects the metabolism of carbohydrates, proteins, and fats.

Synthesis: Synthesized by beta cells in the pancreas in response to high blood glucose levels.
Secretion: Pancreas secretes approximately 30 units of insulin daily, both basally and in response to meals.
Proinsulin Cleavage: Proinsulin is cleaved into insulin and C-peptide, both of which are released from the pancreas.
Insulin Clearance: Insulin is cleared from the body through both liver and kidney filtration.

Liver: Anabolic effects, including glycogen synthesis, protein synthesis, and triglyceride synthesis. Anti-catabolic effect, inhibiting gluconeogenesis, ketogenesis, and glycogenolysis.
Muscle: Promotes protein synthesis, glycogen synthesis, and glucose uptake.
Adipose Tissue: Promotes triglyceride storage and inhibits lipolysis.

Symptoms: Polyuria (increased urination), polydipsia (increased thirst), and weight loss.
Blood Glucose Levels:
- Fasting plasma glucose: Greater than 7.0 mmol/l.
- 2-hour plasma glucose: Greater than 11.1 mmol/l during a standard 75g oral glucose tolerance test.
- HbA1c (glycated hemoglobin): Greater than 6.5%.
Impaired Fasting Glucose:
- Normal: Less than 5.6 mmol/l.
- Impaired: Between 5.6 mmol/l and 7.0 mmol/l.

Purpose: To diagnose impaired glucose tolerance or diabetes mellitus.
Procedure: Patient ingests 75g of dextrose, and blood glucose levels are measured after 2 hours.
Results:
- Impaired glucose tolerance: 2-hour glucose levels between 7.8 and 11.1 mmol/l.
- Diabetes mellitus: 2-hour glucose levels greater than 11.1 mmol/l.

Type 1 Diabetes (Autoimmune and Idiopathic):
- Absolute insulin deficiency.
- Secondary to pancreatic beta cell destruction.
- Insulin-dependent for survival.
- Associated with anti-GAD antibodies.
Type 2 Diabetes:
- Insulin resistance, leading to hyperinsulinemia.
- Beta cell dysfunction.
- Over 80% of cases associated with obesity.
- Can occur in non-obese individuals, often under 25 years old.
Gestational Diabetes: Diabetes developing during pregnancy.