Diabetes

Question 1

Define the term diabetes mellitus

Answer 1

Chronic hyperglycaemia due to insulin deficiency, insulin resistance or both

Question 2

How does type I diabetes arise?

Answer 2

It’s an autoimmune disease in which killer lymphocytes, macrophages and antibodies attack and destroy beta cells.

Question 3

What is the triad of symptoms for a diabetic?

Answer 3

Polyuria, polydipsia and weight loss

Question 4

Why does polydipsia occur in diabetics?

Answer 4

They lose a lot of water in their urine (due to polyuria) and thus need to keep drinking

Question 5

Why does polyuria occur in diabetics?

Answer 5

Large quantities of glucose in the blood are filtered by the kidney, so not all of it is reabsorbed. Extra glucose in the nephron places extra osmotic load on it, meaning that less water is reabsorbed to maintain osmotic pressure

Question 6

How is type I diabetes diagnosed?

Answer 6

Measurement of plasma glucose levels. Elevated blood glucose because of the lack of insulin

Question 7

What does a lack of insulin cause?

Answer 7

Less uptake of glucose into adipose tissue and skeletal muscle, less storage of glycogen, gluconeogenesis occurs

Question 8

Aside from the triad, what other signs might there be that someone is a type I diabetic?

Answer 8

Glycosuria and ketoacidosis (smelling acetone on the breath)

Question 9

How does type II diabetes arise?

Answer 9

Lack of function in beta-cells, disorders of insulin secretion or insulin resistance thus resulting in hyperglycaemia

Question 10

Briefly describe type I diabetes

Answer 10

Commonest in young people, loss of all or most of pancreatic beta-cells, rapidly fatal, must be treated with insulin

Question 11

Briefly describe type II diabetes

Answer 11

Commonly affects older people, slow progressive loss of beta cells but with disorders of insulin secretion and tissue resistance, not immediately fatal, may not initially need insulin but will eventually.

Question 12

Describe and explain the typical pattern of presentation of type I diabetes

Answer 12

Can be found with relevant HLA markers and auto-antibodies but without insulin abnormalities. May then develop impaired glucose tolerance and then diabetes

Question 13

Describe and explain the typical pattern of presentation of type II diabetes

Answer 13

Found with insulin resistance which can lead to impaired glucose tolerance and finally diabetes.

Question 14

How is diabetes diagnosed?

Answer 14

Venous plasma >11.1mmol/L, fasting plasma glucose >7.0mmol/L, plasma glucose conc >11.1mmol/L 2 hrs after 75g anhydrous glucose or in OGTT (plus symptoms)

Question 15

How can ketoacidosis occur in uncontrolled diabetics?

Answer 15

Increased beta-oxidation in the liver leading to high levels of ketone bodies. H+ associated with ketones can cause ketoacidosis

Question 16

How would a patient with ketoacidosis present?

Answer 16

Prostration, hyperventilation, nausea, vomiting, dehydration and abdominal pain

Question 17

What symptoms would occur if someone was hypoglycaemic?

Answer 17

Sweating, anxiety, hunger, tremor, palpitations, confusion, drowsiness, seizures, coma

Question 18

What is the lower threshold for plasma glucose?

Answer 18

<2 mmol/L - can be fatal as the CNS would not have sufficient glucose

Question 19

What is the upper threshold for plasma glucose?

Answer 19

> 10 mmol/L

Question 20

How is type I diabetes treated?

Answer 20

Insulin injections (peptide hormones would be digested in the stomach). Education of patients - infections, hypoglycaemia etc

Question 21

How is type II diabetes treated?

Answer 21

By diet or oral hypoglycaemic drugs (such as sulphonylureas) which increase insulin release from beta-cells and reduce insulin resistance. Metformin - reduces gluconeogenesis

Question 22

Describe the action of aldose reductase

Answer 22

Catalyses the following reaction in peripheral nerves, eyes and kidney: glucose + NADPH + H+ —> sorbitol + NADP+ (leads to S-S formation)

Question 23

What does the accumulation of sorbitol do?

Answer 23

Causes osmotic damage to cells

Question 24

Describe the HbA1c test

Answer 24

Glucose reacts with terminal valine of Hb to produce HbA1c - indicator of how effective blood glucose control has been ~ 3 months

Question 25

What are the macrovascular complications of diabetes?

Answer 25

Risk of stroke, myocardial infarction, poor circulation to periphery - feet

Question 26

What are the microvascular complications of diabetes?

Answer 26

Retinopathy, neuropathy, nephropathy, diabetic foot

Question 27

How does diabetic retinopathy arise?

Answer 27

Damage to blood vessels in retina which can lead to blindness, vessels can leak or rupture. New vessels (proliferative retinopathy) - weak and can easily bleed

Question 28

How does nephropathy arise?

Answer 28

Damage to glomeruli, poor blood supply because of change in kidney blood vessels, damage from infections of urinary tract. Early sign - microalbuminuria

Question 29

How does neuropathy arise?

Answer 29

Damage to peripheral nerves causing change or loss of function, changes due to alteration in function of ANS

Question 30

How does diabetic foot arise?

Answer 30

Poor blood supply, damage to nerves, increased risk of infection all - gangrene.