Diabetes Mellitus

Question 1

What is diabetes mellitus?

Answer 1

A group of metabolic disorders characterised by chronic hyperglycaemia

Question 2

What is diabetes mellitus due to?

Answer 2

Insulin deficiency, insulin resistance, or both

Question 3

At what age is type 1 diabetes onset most common?

Answer 3

Teenage years

Question 4

Describe the age related rate of type 1 diabetes after teenage years?

Answer 4

It is mostly similar up until old

Question 5

Does the rate of diabetes mellitus type 1 vary between countries?

Answer 5

Yes, substantially

Question 6

What does the strong seasonal variation of type 1 diabetes onset suggest?

Answer 6

A link with viral infection acting as a trigger

Question 7

What is the mechanism of onset of type 1 diabetes?

Answer 7

1. Genetic predisposition to the disease interacts with environmental triggers to produce immune activation
2. Immune activation leads to the production of killer lymphocytes, macrophages and antibodies that attack and progressively destroy ß-cells

Question 8

What is the genetic predisposition to type 1 diabetes associated with?

Answer 8

The genetic markers HLA DR2 and HLA DR4

Question 9

How does a patient present with type 1 diabetes?

Answer 9

• Polyuria
• Polydipsia
• Weight loss

Question 10

What is polyuria?

Answer 10

Excess urine production

Question 11

What produces the polyuria in type 1 diabetes?

Answer 11

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

Question 12

What is polydipsia?

Answer 12

Thirst and drinking a lot, due to polyuria

Question 13

Why does type 1 diabetes cause weight loss?

Answer 13

Fat and protein are metabolised because insulin is absent

Question 14

Describe the typical patient presenting with type 1 diabetes

Answer 14

A lean young person with a recent history of viral infection

Question 15

How can type 1 diabetes be diagnosed?

Answer 15

By measurement of plasma glucose levels

Question 16

Why is blood glucose raised in type 1 diabetes?

Answer 16

Due to lack of insulin

Question 17

How does a lack of insulin cause a rise in plasma glucose?

Answer 17

• Decreased uptake of glucose into adipose tissue and skeletal muscle
• Decreased storage of glucose as glycogen in muscle and liver
• Increased gluconeogenesis in liver

Question 18

What will high blood glucose lead to the appearance of?

Answer 18

Glucose in the urine - glycosuria

Question 19

What will happen if type 1 diabetes is not dealt with rapidly?

Answer 19

The individual will progress to a life-threatening crisis - diabetic ketoacidosis

Question 20

In what populations is type 2 diabetes relatively common?

Answer 20

All those enjoying an affulent lifestyle

Question 21

What is the estimated prevalence of type 2 diabetes in the UK?

Answer 21

About 2% of the population

Question 22

In whom is type 2 diabetes most common in?

Answer 22

Older and overweight people

Question 23

What % of their ß-cells to patients with type 2 diabetes retain at diagnosis?

Answer 23

About 50%

Question 24

What happens to the ß-cell levels in patients with type 2 diabetes over time?

Answer 24

The levels fall, ultimately to none, and patients develop disorders of insulin secretion or insulin resistance, and so blood glucose is raised

Question 25

What is the difference between type 1 and 2 diabetes in terms of age distribution

Answer 25

* Type 1 is the commenest type in the young * Type 2 affects a large number of usually older individuals

Question 26

What is type 1 diabetes characterised by?

Answer 26

The progressive loss of all or most of the pancreatic ß-cells

Question 27

What is type 2 diabetes characterised by?

Answer 27

The slow progressive loss of ß-cells, but with disorders of insulin secretion and tissue resistance

Question 28

Describe the prognosis of type 1 diabetes

Answer 28

It is rapidly fatal if not treated

Question 29

Describe the difference in treatment between type 1 and 2 diabetes

Answer 29

Type 1 diabetes must be treated with insulin, whereas type 2 diabetes may not initially need treatment with insulin, but all do eventually

Question 30

Describe the progression of type 1 diabetes from its onset

Answer 30

1. People can be found with the relevant HLA markers and auto-antibodies, but without glucose or insulin abnormalities 2. They may then develop impaired glucose tolerance 3. They may then develop diabetes (sometimes initially diet controlled) 4. They will eventually become totally insulin dependant

Question 31

Describe the progression of type 2 diabetes

Answer 31

1. People can be found with insulin resistance 2. As insulin production fails, they develop impaired glucose tolerance 3. Finally, they will develop diabetes than can initially be controlled by diet, then tablets, then insulin 4. *If this process continues long enough, they may loose all insulin production*

Question 32

How is a diagnosis of diabetes made?

Answer 32

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*

Question 33

What is required to confirm diabetes in the absense of symptoms?

Answer 33

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*

Question 34

Why is it essential to be secure in a diabetes diagnosis?

Answer 34

A diagnosis of diabetes has important legal and medical implications for the patient

Question 35

What leads to the production of huge amounts of ketone bodies in diabetes?

Answer 35

High rates of ß-oxidation of fats in the liver, coupled with the low insulin/anti-insulin ratio

Question 36

Give three examples of ketone bodies

Answer 36

* Acetoacetone * Acetone * ß-hydroxybutyrate

Question 37

How can it be clinically detected that a patient is producing a large amount of ketone bodies?

Answer 37

Volatile acetone is breathed out, and can be smelt on the patients breath

Question 38

What clinical condition can the production of large amounts of ketone bodies in diabetes lead to?

Answer 38

Ketoacidosis

Question 39

How does the production of large amounts of ketone bodies in diabetes cause ketoacidosis?

Answer 39

Due to the H⁺ associated with ketones

Question 40

What are the features associated with ketoacidosis?

Answer 40

* Prostration * Hyperventilation * Nausea * Vomiting * Dehydration * Abdominal pain

Question 41

When is it very important to test for ketones?

Answer 41

When checking the urine in assessment of diabetes control