Diabetes Mellitus Flashcards
What is diabetes mellitus?
A group of metabolic disorders characterised by chronic hyperglycaemia
What is diabetes mellitus due to?
Insulin deficiency, insulin resistance, or both
At what age is type 1 diabetes onset most common?
Teenage years
Describe the age related rate of type 1 diabetes after teenage years?
It is mostly similar up until old
Does the rate of diabetes mellitus type 1 vary between countries?
Yes, substantially
What does the strong seasonal variation of type 1 diabetes onset suggest?
A link with viral infection acting as a trigger
What is the mechanism of onset of type 1 diabetes?
- Genetic predisposition to the disease interacts with environmental triggers to produce immune activation
- Immune activation leads to the production of killer lymphocytes, macrophages and antibodies that attack and progressively destroy ß-cells
What is the genetic predisposition to type 1 diabetes associated with?
The genetic markers HLA DR2 and HLA DR4
How does a patient present with type 1 diabetes?
- Polyuria
- Polydipsia
- Weight loss
What is polyuria?
Excess urine production
What produces the polyuria in type 1 diabetes?
Large quantities of glucose in the blood are filtered by the kidney, so not all of it is reabsorbed. The extra glucose in the nephron places an extra osmotic load on it, meaning that less water is reabsorbed to maintain osmotic pressure
What is polydipsia?
Thirst and drinking a lot, due to polyuria
Why does type 1 diabetes cause weight loss?
Fat and protein are metabolised because insulin is absent
Describe the typical patient presenting with type 1 diabetes
A lean young person with a recent history of viral infection
How can type 1 diabetes be diagnosed?
By measurement of plasma glucose levels
Why is blood glucose raised in type 1 diabetes?
Due to lack of insulin
How does a lack of insulin cause a rise in plasma glucose?
- Decreased uptake of glucose into adipose tissue and skeletal muscle
- Decreased storage of glucose as glycogen in muscle and liver
- Increased gluconeogenesis in liver
What will high blood glucose lead to the appearance of?
Glucose in the urine - glycosuria
What will happen if type 1 diabetes is not dealt with rapidly?
The individual will progress to a life-threatening crisis - diabetic ketoacidosis
In what populations is type 2 diabetes relatively common?
All those enjoying an affulent lifestyle
What is the estimated prevalence of type 2 diabetes in the UK?
About 2% of the population
In whom is type 2 diabetes most common in?
Older and overweight people
What % of their ß-cells to patients with type 2 diabetes retain at diagnosis?
About 50%
What happens to the ß-cell levels in patients with type 2 diabetes over time?
The levels fall, ultimately to none, and patients develop disorders of insulin secretion or insulin resistance, and so blood glucose is raised
What is the difference between type 1 and 2 diabetes in terms of age distribution
- Type 1 is the commenest type in the young
- Type 2 affects a large number of usually older individuals
What is type 1 diabetes characterised by?
The progressive loss of all or most of the pancreatic ß-cells
What is type 2 diabetes characterised by?
The slow progressive loss of ß-cells, but with disorders of insulin secretion and tissue resistance
Describe the prognosis of type 1 diabetes
It is rapidly fatal if not treated
Describe the difference in treatment between type 1 and 2 diabetes
Type 1 diabetes must be treated with insulin, whereas type 2 diabetes may not initially need treatment with insulin, but all do eventually
Describe the progression of type 1 diabetes from its onset
- People can be found with the relevant HLA markers and auto-antibodies, but without glucose or insulin abnormalities
- They may then develop impaired glucose tolerance
- They may then develop diabetes (sometimes initially diet controlled)
- They will eventually become totally insulin dependant
Describe the progression of type 2 diabetes
- People can be found with insulin resistance
- As insulin production fails, they develop impaired glucose tolerance
- Finally, they will develop diabetes than can initially be controlled by diet, then tablets, then insulin
- If this process continues long enough, they may loose all insulin production
How is a diagnosis of diabetes made?
The presence of symptoms, i.e. polyuria, polydipsia, and unexplained weight loss, plus;
- A random venous plasma glucose >11.1mmol/L, or
- A fasting plasma glucose concentration of >7.0mmol/L or
- A plasma glucose concentration >11.1mmol/L 2 hours after 75g anhydrous glucose in an oral glucose tolerance test
With no symptoms, diagnosis should not be based on a single glucose determination, but requires conformatory venous plasma glucose determination
What is required to confirm diabetes in the absense of symptoms?
At least one additional glucose test result on another day with a value in the diabetic range, either fasting, from a random sample, or from two hours post glucose load
Why is it essential to be secure in a diabetes diagnosis?
A diagnosis of diabetes has important legal and medical implications for the patient
What leads to the production of huge amounts of ketone bodies in diabetes?
High rates of ß-oxidation of fats in the liver, coupled with the low insulin/anti-insulin ratio
Give three examples of ketone bodies
- Acetoacetone
- Acetone
- ß-hydroxybutyrate
How can it be clinically detected that a patient is producing a large amount of ketone bodies?
Volatile acetone is breathed out, and can be smelt on the patients breath
What clinical condition can the production of large amounts of ketone bodies in diabetes lead to?
Ketoacidosis
How does the production of large amounts of ketone bodies in diabetes cause ketoacidosis?
Due to the H+ associated with ketones
What are the features associated with ketoacidosis?
- Prostration
- Hyperventilation
- Nausea
- Vomiting
- Dehydration
- Abdominal pain
When is it very important to test for ketones?
When checking the urine in assessment of diabetes control
