Diabetes Mellitus

Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management | Complications

Definition

Diabetes mellitus is a chronic metabolic disorder characterised by hyperglycaemia due to insulin deficiency, insulin resistance, or both.

Aetiology

  • Type 1 diabetes mellitus: autoimmune destruction of pancreatic beta cells, leading to absolute insulin deficiency.
  • Type 2 diabetes mellitus: insulin resistance with progressive pancreatic beta-cell dysfunction.
  • Gestational diabetes: glucose intolerance first diagnosed during pregnancy.
  • Secondary diabetes: caused by endocrinopathies (e.g., Cushing’s syndrome, acromegaly), pancreatic diseases, or medications (e.g., steroids, antipsychotics).

Pathophysiology

  • Type 1 diabetes: autoimmune-mediated beta-cell destruction results in loss of insulin production.
  • Type 2 diabetes: insulin resistance in peripheral tissues leads to compensatory hyperinsulinaemia; beta-cell failure eventually occurs.
  • Chronic hyperglycaemia leads to endothelial dysfunction, oxidative stress, and systemic complications.

Risk Factors

  • Family history of diabetes.
  • Obesity and sedentary lifestyle.
  • Hypertension and dyslipidaemia.
  • Polycystic ovary syndrome (PCOS).
  • History of gestational diabetes.
  • Ethnicity (higher prevalence in South Asian, African, and Hispanic populations).

Signs and Symptoms

  • Classic symptoms: polyuria, polydipsia, polyphagia, weight loss.
  • Fatigue and blurred vision.
  • Frequent infections: recurrent fungal infections, UTIs.
  • Delayed wound healing.
  • Diabetic ketoacidosis (DKA): acute presentation in type 1 diabetes with nausea, vomiting, Kussmaul breathing.
  • Hyperosmolar hyperglycaemic state (HHS): severe dehydration and altered mental status in type 2 diabetes.

Investigations

  • Fasting plasma glucose (FPG): ≥7.0 mmol/L indicates diabetes.
  • HbA1c: ≥48 mmol/mol (6.5%) confirms diabetes.
  • Oral glucose tolerance test (OGTT): 2-hour plasma glucose ≥11.1 mmol/L confirms diabetes.
  • Random plasma glucose: ≥11.1 mmol/L in symptomatic patients.
  • Urine dipstick: checks for glycosuria and ketonuria.
  • Lipid profile and renal function: assess for metabolic syndrome and nephropathy.

Management

1. Lifestyle Modifications:

  • Dietary changes: reduce refined carbohydrates, increase fibre and healthy fats.
  • Regular exercise: at least 150 minutes of moderate-intensity activity per week.
  • Weight management: aim for BMI <25 kg/m².

2. Pharmacological Therapy (follow local guideline- see below example):

  • Metformin: first line therapy for type 2 diabetes.
  • SGLT2 inhibitors (e.g., empagliflozin) if Qrisk>10%: reduce cardiovascular risk. But ensure you discuss s/e such as Fournier’s gangrene.
  • GLP-1 receptor agonists (e.g., liraglutide): promote weight loss and glucose control.
  • Insulin therapy: required for type 1 diabetes and advanced type 2 diabetes.

3. Monitoring:

  • Regular HbA1c checks every 3–6 months.
  • Annual screening for diabetic retinopathy, nephropathy, and neuropathy.

Complications

1. Microvascular Complications:

  • Diabetic retinopathy: vision loss due to retinal damage.
  • Diabetic nephropathy: progressive kidney disease leading to renal failure.
  • Diabetic neuropathy: peripheral neuropathy causing pain, numbness, foot ulcers.

2. Macrovascular Complications:

  • Coronary artery disease: increased risk of myocardial infarction.
  • Peripheral arterial disease: increased risk of amputations.
  • Stroke: elevated risk of cerebrovascular events.

3. Acute Complications:

  • Diabetic ketoacidosis (DKA): life threatening emergency in type 1 diabetes.
  • Hyperosmolar hyperglycaemic state (HHS): severe dehydration in type 2 diabetes.

4. Referral:

  • Endocrinology: for complex cases or insulin initiation.
  • Ophthalmology: if retinopathy is detected.
  • Nephrology: in cases of advanced diabetic nephropathy.
  • Podiatry: for foot ulcer management.
EndocrinologymypanotesDiabetes Mellitus