Diabetes and hypoglycaemia

Question 1

what is the importance of c-peptides in diagnosis? (3marks)

Answer 1

B-cells synthesise insulin as a pro-hormone, c-peptide cleavage leads to the release of mature insulin when blood glucose levels are low. c-peptide is used as a B-cell function marker and index of insulin secretions.
Direct measurement of endogenous insulin by immunoassay in patients undergoing insulin therapy provides inaccurate results because they develop insulin antibodies. c-peptide therefore gives only endogenous levels of insulin as the level present correlates with endogenous insulin released. It’s used to diagnose hypoglycaemia.

Question 2

results of an insulin deficiency and effects to the body (2marks)

Answer 2

causes increase in hepatic output and impaired glucose uptake, causing hyperglycaemia therefore diabetes, glycosuria affecting kidneys causing potential renal failure, ketoacidosis as beta-oxidation of fatty acids increase

Question 3

how is oral glucose tolerance test carrier out? (2marks)

Answer 3

blood sample obstained at 0mins and then 120mins after administering patient with 75g of oral glucose.
Result <7.8mmol/L = normal
a 3 day fasting test is carried out on subject following normal diet with >250g carbs daily

Question 4

list 2 circumstances in which oral glucose tolerance tests are used (1mark)

Answer 4

carried out to determine glucose tolerance status in patients with impaired fasting glucose (6.1-6.9mml/L)
unexplained glycosuria

Question 5

how does gestational pregnancy occur? (2marks)

Answer 5

during pregnancy, placenta releaseshuman placental lactogen –> making mother less sensitive to insulin –> increase in blood glucose so that the foetus gets enough nutrients especially from the 2nd trimester, it also causes maternal levels to exceed normal –> hence termed gestational pregnancy

Question 6

what is ketoacidosis and when does this occur? (2marks)

Answer 6

deficiency in insulin causing excess lipolysis, leading to to ketone body formation and metabolic acidosis, most commonly seen in type 1 diabetes due to insulin insufficiency

Question 7

how does an individual adapt to hypoglycaemia? (2marks)

Answer 7

a drop in insulin levels prevents glucose storage in tissues, stimulating gluconeogenesis and glycogenolysis by liver, increased lipolysis and proteolysis induced by counter-regulatory hormones, cortisol, adrenaline

Question 8

explain 2 deficiencies causing inherited metabolic disorders (4marks)

Answer 8

Galactosaemia: deficiency in GAL-1- PUT causes lack of galactose-1- phosphate conversion to glucose. G1P accumulates in liver causing toxicity

Glycogen storage disease: deficiency in glucose-6- phosphatase in liver blocks

glycogenolysis and gluconeogenesis. Causes hepatomegaly as glycogen accumulates in liver

OR

Hereditary fructose intolerance: fructose-1- phosphate aldolase B deficiency in which F-1- P conversion for glycolysis and gluconeogenesis is impaired so fructose

Question 9

name 3 hormones that oppose insulin (3marks)

Answer 9

cortisol
adrenaline
growth hormone

Question 10

function of liver in regulating blood glucose levels (2marks)

Answer 10

in fed state, liver stores glucose by conversion to glycogen.
during starvation, liver induces gluconeogenesis from lipolysis and proteolysis as well as glycogenolysis from stores by enzyme glucagon