Getting the best marks
Read the whole question – a latter section may give you a
clue about an earlier one.
To see how many points you need look at the marks
allocated – for example a 3 point question is generally looking for 3 salient points
If giving a list answer put the best answers first – examiners will not usually mark answers too
far down a list
Always write something – it may get you part of a mark and is anonymised so
no one will think you are stupid!
If you genuinely have no clue then re-write the question to see if this sparks
some ideas.
If not then move on and come back at the end. And remember – always
write something.
Good luck!
Question 7
Dennis, a 17 year old boy presents with weight loss and
constant tiredness.
Q7.1• List 3 differentials (3)
Q7.2• List the three most
important blood tests (3)
Question 7
Dennis is diagnosed with Type 1
diabetes mellitus.
Q7.3• List differences
between diabetes mellitus Types 1 and 2 (3)
Question 7
In this disease less insulin is produced
Q7.4• List three functions of
insulin (3)
Q7.5• Where is insulin
produced? (2)
Question 7
In this disease less insulin is produced
Q7.6• Describe the structure of
the active insulin molecule (3)
Q7.7• List the stages by which
insulin is produced (6)
Question 7
• One class of drug used to treat diabetes are sulphonyureas – their mechanism is well understood.
Q7.8• Explain the
mechanism of action of sulphonylureas (4)
Q7.9• List another drug that
can be used to control diabetes and its mode of action (3)
Question 7
Dennis’ attitude towards his illness leads to handicap.
Q7.10• Describe the
differences between a disability and a handicap (3)
The Answers
View these on ‘note view’ rather than on full screen – additional
notes are provided for some slides
Generating Differentials:I’D GET VINO…
I Infectious / inflammatory
D Degenerative
G Genetic / Idiopathic
E Endocrine
T Trauma
V Vascular
I Iatrogenic / ingested
N Neoplastic
O Organs
Diabetes
• Pancreatic Islets• 60% beta cells
– Secrete insulin
• 25% alpha cells– Secrete glucagon
• Reciprocal action of hormones– Not usually present
together
• Secretions enter pancreatic vein into portal system
Diabetes
Type 1• Childhood• Often thin• Failure insulin prod.• Insulin dependent
Type 2• Traditionally older• Often overweight• Insulin resistance• Lifestyle/drugs/insulin
Functions of Insulin
Anabolic
• Promotes glucose uptake
• Promotes use of glucose as a fuel
• Promotes K+ uptake– Used to treat
hyperkalaemia
• Protein synthesis
• Blood proteins
• Muscle tissue
• TAG synthesis
• Glycogen synthesis
• Decreased proteolysis
• Decreased lipolysis
• Decr. gluconeogenesis
Insulin
Peptide hormone• Alpha chain
– Species specific
• Beta chain– Biologic activity
• C-peptoid joins chains
Packaging and Release
Insulin production• Increased by glucose
– Transcription
– Translation
• Pre-proinsulin– Signal peptide cleaved
• Proinsulin– Disulphide links
– Excision of C-peptide
• Insulin
• Packaged in Golgi into secretory granules– Insulin– C-peptide
• Insulin forms hexamers
• Secreted via exocytosis
Release of Insulin
• GLUT-2 admits glucose– Keeps intracellular conc
same as interstitial fluid
• ATP prod stimulated• ATP:ADP ratio changes• ATP binds to K+ channel• Channel closes• Cell depolarisation
• Depolarisation– Opening of voltage
gated Ca++ channels– Increased [Ca++]
• Exocytosis– Release of insulin
Depolarisation
SUR1SUR1
SUR1SUR1
Sulphonylurea Molecules
Ca++
Ca++
Ca++ Ca++
Ca++Ca++
Ca++
Ca++
Ca++Ca++
Ca++
Insulin Vesicle
SUR1SUR1
SUR1SUR1
Sulphonylurea Molecules
Ca++
Ca++
Ca++ Ca++
Ca++
Ca++
Ca++
Ca++Ca++
Ca++
Insulin Vesicle
Insulin
Other Drugs
Metformin• Unknown mechanism• Gluconeogenesis• Insulin sensitivity• No weight gain• Epigastric discomfort• Diarrhoea• Anorexia
Glitazones• Alpha ketoglutarase
inhibitor• carbohydrate
breakdown in gut• Abdominal discomfort• Diarrhoea• Flatulence