Diabetes mellitus

Back to endocrinology

These are a group of diseases which were named for two key features:

• Diabetes = Significant polyuria (excessive volumes of urine)
• Mellitus = Glycosuria (urine with a high concentration of glucose) 

 

 Symptoms

• Polyuria
• Polydipsia
• Fatigue
• Weight loss
• Frequent infections
• Frequent urinary tract infections (UTIs) 
• Slow wound healing
• Blurred vision
• Skin ulceration

 

Pathophysiology

• Every type of diabetes mellitus involves insufficient insulin signalling.
• There is insufficent transport of glucose into cells.
• There is hyperglycaemia (excessive blood glucose concentrations).
• The low intracelullar glucose concentration results in intracellular glycogen deficiency.
• A proportion of glucose leaves the blood in the kidney and enters the urine. Consequently, with hyperglycaemia, there will be glycosuria.
• Urine containing an abnormally high concentration of glucose has an abnormally high osmotic pressure. An abnormally large volume of water is held within the urine. This results in polyuria.
• Due to the polyuria, dehydration may develop. This causes polydipsia (excessive thirst).

 

Etymology

• Diabetes: from Greek diabainein (to go through). A pathological state in which a patient produces excessive volumes of urine and drinks excessive amounts of fluid to compensate. 
• Diabetes mellitus: From Latin mellītus (sweet). Blood glucose levels are excessively high for prolonged periods. This leads to excessive thirst and excretion of large volumes of urine with a high glucose concentration (sweet urine).

 

Types

Classically DM is classified into 3 types. This is certainly an oversimplification, since there are many causes. In one study, data analysis revealed 5 significantly distinct groups of DM. It was suggested that DM should be classified as no fewer than 5 diseases. However it will take many years for this model to become widespread.

For simplicity, this blog will use the 3-type overview.

• Diabetes mellitus type 1 : consequence of beta-cell (pancreatic islets) destruction
• Diabetes mellitus type 2 : consequence of insulin resistance
• Gestational diabetes : consequence of pregnancy

 

Complications

Acute

• Diabetic hypoglycaemia
• Diabetic coma
• Diabetic ketoacidosis
• Hyperosmolar hyperglycaemic state
• Stroke
• Myocardial infarction

Chronic

• Diabetic vasculopathy
• Diabetes mellitus associated infectious diseases
• Impaired wound healing

During pregnancy

• Fetal macrosomia

 

Investigations

• HbA1c