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Practical Revision > Glucose Tolerance > Flashcards

Glucose Tolerance Flashcards

1
Q

List 6 major energy sources for body tissues

A 
Glucose
FAs
AAs
Pyruvate/lactate
Glycerol
Ketone bodies
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2
Q

Explain “caloric homeostasis”

A

When the metabolic processes in a body ensure the overall maintenance and balance of different fuel sources, the body is in a state of caloric homeostasis

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3
Q

What is the ideal range for blood glucose?

A

3.9-5.6mM

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4
Q

What is the ideal range for energy sources excluding glucose?

A

Most (e.g. lactate, FAs, ketone bodies) can vary over an enormous range

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5
Q

List the major users of glucose

A

Brain
RBCs
Skeletal muscle

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6
Q

Why is strict control of blood glucose necessary?

A

Because the brain has an absolute requirement for glucose as an energy source

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7
Q

At what blood glucose level would hypoglycaemic coma occur? Why?

A

<1.5mM

Lack of ATP available to brain

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8
Q

List 3 possible consequences of hyperglycaemia

A

Loss of glucose in the urine
Inappropriate glycosylation of proteins
Hyperglycaemia coma

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9
Q

List 3 processes which increase blood glucose

A

Absorption of CHOs from the intestine
Glycogenolysis
Gluconeogenesis (glucose production from non-CHO sources)

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10
Q

List 3 processes which decrease blood glucose

A

Glycolysis
Glycogenesis
Lipogenesis

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11
Q

What is the ideal range for fasting blood glucose in a healthy individual? What is the acceptable range?

A
  1. 9-5.6mM

3. 3-7.2mM

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12
Q

Describe the control of blood glucose post-prandially

A

Dietary glucose is absorbed and transported to the liver via the portal vein
When glucose leaves the liver and enters the systemic circulation, blood glucose increases
Insulin is realised from the pancreatic B cells in response and acts to lower blood glucose

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13
Q

Describe 2 ways in which insulin lowers blood glucose

A

Decreases the release of glucose from the liver (inhibits glycogenolysis and gluconeogenesis, and stimulates glycogenesis)
Increases glucose uptake and utilisation by peripheral tissues (e.g. muscle, adipose)

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14
Q

How is blood glucose maintained in the fasting state?

A

Glucose is predominantly supplied by the liver through breakdown of its glycogen stores and by gluconeogenesis from lactate, glycerol and AAs (small amount is contributed by kidney)

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15
Q

Why can liver and kidney produce glucose, but not skeletal muscle?

A

Liver and kidney contain the enzyme glucose-6-phosphatase, necessary for the conversion of glucose-6-phosphate to glucose

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16
Q

What are the hormonal mechanisms which prevent an excessive fall in blood glucose during fasting?

A

Glucagon promotes glycogenolysis in the liver and gluconeogenesis in the liver and kidney
Adrenaline promotes (some) glycogenolysis and gluconeogenesis, and (all) glycogenolysis in the skeletal muscle
Cortisol and GH inhibit utilisation of glucose by peripheral tissues (cortisol also acts with glucagon to stimulate gluconeogenesis)

17
Q

What is the difference between whole blood FBG levels and serum/plasma values? Why?

A

FBG normal range in whole blood is 3.9-5.6mM

Serum or plasma values are ~12% higher because the haematocrit contributes ~12% to the volume of whole blood

18
Q

Does plasma have glycolytic activity? What about blood cells? Why is this important in the context of measuring blood glucose?

A

Plasma has no glycolytic activity
Blood cells are capable of considerable glycolysis even at room temperature
Unless glucose is to be determined immediately, blood should be collected in a mixture of sodium fluoride and sodium oxalate (or heparin) to inhibit glycolysis and coagulation respectively

19
Q

How do diabetic patients monitor their glucose levels?

A

On a regular basis, using an automated analyser which requires a minimal blood sample and provides a digital readout of the glucose concentration

20
Q

What does a glucose tolerance curve chart?

A

Change in blood glucose levels with time after ingestion of a glucose load

21
Q

Describe the magnitude and duration of the temporary rise in blood glucose post-prandially in normal, healthy individuals. What is the maximum post-prandial blood glucose level in these individuals and what is the maximum duration of this increase? What is the peak blood glucose level?

A

Varies depending on the type and quantity of food taken
Maximum level does not usually exceed 9-10mM and returns to fasting level within 3 hours
Peak blood glucose level in healthy persons does not exceed the renal threshold (10-11mM)

22
Q

What would the glucose tolerance curve for an individual with mild or diet-controlled diabetes look like?

A

FBG may be within the normal range
However, unable to produce sufficient insulin for prompt metabolism of carbohydrate, leading to an abnormally high peak blood glucose post-prandially and a delay in the return to normal levels
May be some glucosuria

23
Q

Describe the glucose tolerance curve for a normal, healthy individual

A

Initial blood glucose would be within normal fasting range
Rise to between 7.2-8.9mM at 30-60mins post-prandial
Return to normal fasting range within 90-180min
No glucosuria

24
Q

Describe the glucose tolerance curve in an individual with diminished glucose tolerance

A

Fasting glucose may be above normal
Peak glucose greater than normal (can be >28mM in untreated DM)
Return to fasting level is delayed

25
Q

Give 4 examples of endocrine disorders which can lower glucose tolerance

A

DM
Hyperpituitarism
Hyperthyroidism
Hyperadrenalism (specifically hypercortisolism/Cushing’s syndrome)

26
Q

Diseases of which 2 organs can also diminish glucose tolerance?

A

Liver

Kidney

27
Q

What is renal glucosuria?

A

A condition in which the renal threshold is lowered so that glucose is excreted in the urine, even though the blood sugar curve is normal

28
Q

Describe the glucose tolerance curve in an individual with increased glucose tolerance

A

Little rise in the blood glucose level throughout the test

29
Q

List 4 conditions in which there may be a flat glucose tolerance curve (i.e. in which there is increased glucose tolerance)

A

Hypopituitarism
Hypothyroidism
Hypoadrenalism (specifically hypocortisolism/Addison’s disease)
Malabsorption syndrome

30
Q

List 5 symptoms of lactose malabsorption

A 
Diarrhoea
Abdominal pain and/or discomfort
Bloating
Borborygmi (stomach rumbling)
Flatulence
31
Q

How is the glucose tolerance test performed?

A

Patient fasts the night before
CHO load is administered (1g/kg body weight, but not more than 75g)
Blood glucose is measured at 0, 30, 60, 90 and 120 mins
Urine is measured at 45 mins

Practical Revision (7 decks)

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