Principles of endocrine disease and its assessment

Question 1

Where do peptide hormones act and why?

Answer 1

→ surface receptors because they are charged

Question 2

Where do steroid hormones act and why?

Answer 2

→ nuclear receptors because they are aliphatic

Question 3

What type of hormone is thyroid hormones?

Answer 3

→ steroid

Question 4

What type of testing do you have to use for hormones and why?

Answer 4

→ dynamic

→ Hormones are pulsatile and vary during the day

Question 5

How do you do a radioimmunoassay in the lab?

Answer 5

→ a labelled hormone that is a marker (radioactive)
→ antibody
→ Limited number of binding sites
→ centrifuge and measure how much radioactivity is in the bound fraction
→ do a standard curve

Question 6

What is an advantage of a total hormone assay?

Answer 6

→ cheap

Question 7

What are 2 disadvantages of a total hormone assay?

Answer 7

→ Hormones are found bound to proteins which affects the measurements and is not reflective of the true amount of hormone

Question 8

Why is the total amount of hormone not a true indicator?

Answer 8

→ Only hormones that are not bound to protein have a true effect

Question 9

What are advantages of a free hormone assay?

Answer 9

→ Representative of active hormone fraction

→ Not binding protein dependant

Question 10

What are disadvantages of a free hormone assay?

Answer 10

→ Complex and expensive

→ Can have poor reproducibility

Question 11

If you have more steps in an assay what does this do to the accuracy?

Answer 11

→ decreases the accuracy

→ transfer errors

Question 12

How do you separate free hormones in an assay?

Answer 12

→ dialysis membrane

→ causing binding protein to precipitate out

Question 13

What does the radiometric assay work on?

Answer 13

→ on peptide hormones

Question 14

Why is measuring a peptide hormone difficult?

Answer 14

→ Peptide hormones have a very short half life
→ Enzymes cleave them
→ you have fragments of them in the circulation

Question 15

How does a radiometric assay work?

Answer 15

→ antibody binds to amide end
→ sticks to test tube
→ wash test tube

Question 16

How does tri iodothyronine get produced?

Answer 16

→ TRH is released from the hypothalamus
→ goes to the pituitary and causes the release of TSH
→ TSH acts on the thyroid
→ tri-iodothyronine is the biologically active hormone

Question 17

How do you measure overproduction of thyroid hormone?

Answer 17

→ autoantibodies
→ Technetium scanning
→ Thyroid function

Question 18

How do you measure underproduction of thyroid hormone?

Answer 18

→ Thyroid function

→ Autoantibodies

Question 19

How do you check for thyroiditis?

Answer 19

→ Thyroid function
→ ESR
→ Technetium

Question 20

Why is thyroiditis sometimes mistaken for overproduction of thyroid hormone?

Answer 20

→ thyroid has about 18 months worth of thyroid hormone stored
→ If it gets infected it becomes leaky and releases the hormone

Question 21

What do you measure if there is a suspected thryoid nodule?

Answer 21

→ Ultrasound

→ Fine needle aspiration biopsy

Question 22

What is the diagnosis if T4 is high and TSH is high?

Answer 22

→ Check peripheral hormone
→ high - hyperthyroidism
→ decide whether primary or secondary
→ if T4 is high then TSH should be low (inhibits)
→ Has not happened so the problem is secondary

Question 23

What is the negative feedback mechanism of thyroxine?

Answer 23

→ TSH sent to thyroid
→ Thyroid produces T3 and T4
→ T4 is end hormone so it inhibits TSH

Question 24

If T4 and T3 is high and TSH is low what is the diagnosis?

Answer 24

→Hyperthyroidism
because peripheral hormones are high
→ primary because the TSH is low - correct functioning of the brain

Question 25

If TSH is high and T3 and T4 are low what is the diagnosis?

Answer 25

→ Hypothyroidism
→Less negative feedback
→ TSH should increase
→ Primary because TSH is high - correct brain function

Question 26

If TSH is low and T3 and T4 are low what is the diagnosis?

Answer 26

→ Hypothyroidism
→ TSH should increase
→ brain function incorrect
→ Secondary

Question 27

If T4 is low, TSH is low and T3 is normal what is the diagnosis?

Answer 27

→ Sick Euthyroid

Question 28

How should the dexamethasone suppression test be in normal people?

Answer 28

→ Cortisol level should decrease below 50

→ high dose should be 50% of baseline

Question 29

Dethamethasone test in people with cushings disease?

Answer 29

→ low dose = not below 50
→high dose = more than 50% decrease
→ ACTH are high

Question 30

Dexamethasone test in people with adrenal tumor?

Answer 30

→ low dose = not below 50
→ high dose = less than 50% decrease
→ ACTH is low

Question 31

Dexamethasone test in people with ectopic ACTH?

Answer 31

→ low dose = more than 50
→ high dose = less than 50 decrease
→ ACTH very high

Question 32

How do you test for Addisons?

Answer 32

→give synthetic ACTH

→ Cortisol level rises

Question 33

What is the short synacthen test?

Answer 33

→ Shot of ACTH
→ Cortisol goes above 400
→ Diagnose adrenal failure

Question 34

What is the long synacthen test used for?

Answer 34

→Blood taken over 24 hours

→ Diagnose secondary adrenal failure

Question 35

What happens in the long synacthen test if it is pituitary vs Addisons?

Answer 35

→ Cortisol levels rise
→ can cause growth of adrenal gland

→ if addisons the cortisol wouldn’t be raised

Question 36

What is done to test for growth hormone deficiency?

Answer 36

→ Large insulin dose
→ hypoglycaemia (less than 2.1)
→ cortisol should increase

Question 37

What is the oral glucose tolerance test?

Answer 37

→  test for GH excess
→ 75g oral glucose
→ samples for GH taken 
→ normal individuals GH fall 
→ Acromegaly = rise

Question 38

If the hormone is too high how do you test?

Answer 38

→ Suppress it

Question 39

If the hormone is too low how do you test for it?

Answer 39

→ Stimulate it