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Diabetes mellitus type 1

Medicine > Endocrine & metabolic

Background knowledge 🧠

Definition

  • Type 1 diabetes mellitus (T1DM) is an autoimmune condition characterised by destruction of insulin-producing beta cells in the pancreas.
  • Leads to absolute insulin deficiency and hyperglycaemia.
  • Requires lifelong insulin therapy.
  • Previously known as juvenile-onset diabetes.

Epidemiology

  • Incidence: approximately 10-20 per 100,000 per year in the UK.
  • More common in Caucasians.
  • Typically presents in childhood or early adulthood.
  • Slightly more common in males than females.
  • Increasing incidence worldwide.

Aetiology and Pathophysiology

  • Autoimmune destruction of pancreatic beta cells.
  • Genetic predisposition (e.g., HLA-DR3 and HLA-DR4).
  • Environmental triggers (e.g., viral infections).
  • Results in absolute insulin deficiency.
  • Leads to hyperglycaemia, ketoacidosis, and other metabolic disturbances.

Clinical Features 🌡️

Symptoms

  • Polyuria (frequent urination).
  • Polydipsia (excessive thirst).
  • Polyphagia (increased hunger).
  • Weight loss.
  • Fatigue.
  • Blurred vision.
  • Recurrent infections.
  • Ketoacidosis (in severe cases).

Signs

  • Signs of dehydration (e.g., dry mucous membranes, reduced skin turgor).
  • Ketotic breath (fruity smell).
  • Rapid, deep breathing (Kussmaul respirations).
  • Tachycardia.
  • Hypotension (if dehydrated).
  • Altered mental status (in severe cases).
  • Weight loss and muscle wasting.

Investigations 🧪

Tests

  • Fasting blood glucose (≥7.0 mmol/L).
  • Random blood glucose (≥11.1 mmol/L with symptoms).
  • HbA1c (≥48 mmol/mol).
  • Urinalysis (glucosuria, ketonuria).
  • C-peptide levels (low or undetectable).
  • Autoantibody testing (e.g., GAD, IA-2, ZnT8).
  • Venous blood gas and capillary ketones (if DKA is suspected).
  • Electrolytes and renal function tests.

Diagnostic Criteria

  • Diabetes symptoms plus one positive test:
    • Random blood glucose ≥ 11.1 mmol/l.
    • Fasting blood glucose ≥ 7.0 mmol/l .
    • Oral glucose tolerance test (OGTT) ≥ 11.1 mmol/l.
  • No symptoms plus two positive tests.

Management 🥼

Management

  • Lifelong insulin therapy (basal-bolus regimen or insulin pump).
  • Regular blood glucose monitoring.
  • Dietary management and carbohydrate counting.
  • Education on hypoglycaemia recognition and management.
  • Management of diabetes-related complications (e.g., retinopathy, nephropathy).
  • Regular follow-up with a diabetes care team.
  • Sick day rules and management of intercurrent illnesses.
  • Psychological support and counselling.
  • Exercise advice and support.

Complications

  • Diabetic ketoacidosis (DKA).
  • Hypoglycaemia.
  • Microvascular complications (retinopathy, nephropathy, neuropathy).
  • Macrovascular complications (cardiovascular disease, stroke).
  • Infections (e.g., candidiasis, skin infections).
  • Foot problems (ulcers, infections).
  • Psychological issues (e.g., depression, anxiety).

Prognosis

  • With appropriate management, individuals with T1DM can lead normal, healthy lives.
  • Lifelong monitoring and treatment are necessary.
  • Risk of complications increases with poor glycaemic control.
  • Early detection and management of complications improve outcomes.
  • Support from a multidisciplinary team is crucial.
  • Advances in technology (e.g., continuous glucose monitors, insulin pumps) have improved quality of life.

Key Points

  • Type 1 diabetes mellitus is an autoimmune condition leading to absolute insulin deficiency.
  • Management includes lifelong insulin therapy, regular monitoring, and lifestyle modifications.
  • Early recognition and treatment of complications are essential to prevent long-term morbidity.
  • Patient education and support from a multidisciplinary team are crucial for optimal management.
  • With appropriate management, individuals with T1DM can lead normal, healthy lives.

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Endocrine & metabolic