Clinical Chemistry

Question 1

What are the clinical features of Diabetic Ketoacidosis?

Answer 1

Low bp
Tachycardia
Low sodium (fluid depletion)
Low bicarbonate/pH and low pC02 consistent with a metabolic acidosis
Disproportionate increase in urea/creatinine suggestive of dehydration
Marked hyperglycaemia

Question 2

What is the pathogenic pathway of diabetic ketoacidosis?

Answer 2

Insulin deficiency leading to preferential metabolism of free fatty acids/ketones and increased glucose production

Glycosuria leads to an osmotic diuresis and fluid depletion

Decreased plasma volume leads to renal hypoperfusion and pre-renal uraemia (dehydration)

Question 3

What is the treatment for diabetic ketoacidosis?

Answer 3

Saline
Insulin
Potassium supplements to correct for development of hypokalaemia
Bicarbonate seldom required

Question 4

What are the principles of the glucose tolerance test?

Answer 4

Unrestricted diet for 3 days prior to test
8-14hr overnight fast
Fasting glucose
75g anhydrous glucose in 250-300ml water in 5mins
Glucose measurement after 2hours

Question 5

What is HONK?

Answer 5

Hyperosmolar non-ketotic hyperglycaemia
Serum osmolality reflects high glucose causing an osmotic diuresis
Leads to reduced glomerular filtration with retention of urea/creatinine
Plasma sodium reflects loss of water in excess of sodium
Occurs only in Type 2 DM
Sufficient insulin produced to prevent excessive lipolysis and oppose ketogenic action of glucagon.
Glucose concentrations generally higher than in DKA

Question 6

How is HONK treated?

Answer 6

Rehydration/insulin are the most essential aspects of treatment (isotonic saline)
Potassium supplements
Prophylactic heparin to prevent thrombosis
Careful monitoring of glucose/fluid balance
Insulin seldom required once acute illness over (diet and/or oral hypoglycaemics)

Question 7

How does the Short Syncthen Test work?

Answer 7

Test of adrenal reserve
9.00am cortisol (+ACTH)

250mg tetracosactrin

Collect samples for cortisol at 30mins

Rise of >220nmol/L and 30min value of at least 550nmol/L

Question 8

What are the features of Addisons Disease and how is it treated?

Answer 8

Life threatening condition
Autoimmune/TB/Iatrogenic 
Can be precipitated by stress
Glucocorticoid/mineralocorticoid deficiency
Treat with hydrocotisone/fludrocortisone
Assess response using cortisol day curve

Question 9

What are the clinical features of Addisons Disease?

Answer 9

Hyperpigmentation
Lack of stress response
Hypotension (postural drop)
Hyponatreamia, Hyperkalaemia, acidosis, Hypercalceamia, Hypoglycaemia
Vomiting, muscle weakness

Question 10

What are the features of Cushings Disease?

Answer 10

Biochemical features due to cortisol excess
Lack of diurnal variation and high 9.00am cortisol and increased 24hour urine cortisol excretion
In cushings disease increased levels of cortisol are required to suppress ACTH
X-ray/MRI or CT to locate source

Question 11

What are the principles of the Dexamethasone suppression test?

Answer 11

First-line screening test for suspected Cushings
Enzyme inducing drugs (anticonvulsants) rapidly metabolise dexamethasone
1mg dexamethasone tablet orally at 23.00hr then take 9am cortisol
Normal response is suppression of 9am cortisol to <50nmol/L

Question 12

What is Conns Syndrome and its causes?

Answer 12

Characterised by excessive aldosterone production

Causes include:
Adrenal adenoma
Bilateral hypertrophy of zona glomerulosa cells
Glucocorticoid remediable hyperaldosteronism

Question 13

What are the clinical features of Conn’s syndrome?

Answer 13

Hypertension, muscle weakness, parasthesia, polydipsia/polyuria

Question 14

What is the diagnostic criteria of the glucose tolerance test?

Answer 14

Fasting glucose >7mmol/L
2 hour glucose >11.1mmol/L
FPG >6.17.8<11.1 Impaired glucose tolerance