Types of Diabetes

To understand the different types of diabetes, it is important to know the definition of Diabetes Mellitus

Diabetes: ‘A metabolic disorder of multiple aetiology characterised by chronic hyperglycaemia with disturbances of carbohydrate, fat, and protein metabolism resulting from absolute or relative(intolerance) insulin deficiency

  • Diabetes is caused by either a deficiency or resistance to insulin (or both)
  • There are 3 main types of diabetes that you will see:
  1. Type 1 DM: Absolute insulin deficiency due to autoimmune destruction of B cells
    • Results in hyperglycaemia and excess gluconeogenesis
  2. Type 2 DM: Insulin resistance+ relative insulin deficiency
    • Either aspect can predominate but bothwill be present
    • Results in hyperglycaemia only
  3. Gestational DM:  Transient hyperglycemia that develops in pregnancy and resolves after delivery

Other types of diabetes  (GAP-DS):

These cause approximately 5% of cases of diabetes

  • Genetic defects of B cell function or insulin action (only one of these that isnt 2º)
  • Pancreatic disease affecting exocrine function (decreasing insulin release)
    • Pancreatitis
    • Trauma
    • Neoplasms
    • Pancreatectomy
  • Excessive hormone Antagonists of insulin
    • Cortisol (Steroids, Cushing’s)
    • Glucagon (glucagonoma)
    • Thyroid hormones (Thyrotoxicosis)
    • Catecholamines (Phaeochromocytoma)
  • Drug-Induced:
    • Beta blockersand thiazidesare key
    • Steroids are a key contributor
    • Atypical antipsychoticse.g. olanzapine
    • Antiretroviral drugs – e.g. acyclovir
    • Transplant drugs – CNIs – result in NODAT
  • Stress hyperglycaemia occurs with acute illnesses
    • Infections
    • MI

This is illustrated in this figure from the ADA