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(erythrocyte sedimentation rate)
→ 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

Question 40

What is involved in screening Cushing's disease testing?

Answer 40

Urinary free cortisol​ Diurnal Rhythm​ Overnight dexamethasone suppression test

Question 41

The Investigation of Cushing’s Disease is in Three Stages​

Answer 41

1. Screening 2. Confirmation of the Diagnosis 3. Differentiation of the cause

Question 42

What is involved in differential diagnosis of Cushing's?

Answer 42

1. True Cushing's 2. Pseudocushing's syndrome 3. exogenous steroids

Question 43

What do results of the CRH test mean?

Answer 43

1. An exaggerated response indicates pituitary dependant Cushing’s Disease​ 2. A flat response indicates ectopic ACTH production​

Question 44

What are some localisation techniques used on different glands?

Answer 44

``` 1. Pituitary​ →MRI​ →Iinferior Petrosa; sinus sampling IPSS​ 2. Adrenal​ →CT or MRI​ 3. Ectopic​ →Octreotide Scan​ →ACTH Sampling ```

Question 45

What are long and short Synacthen tests for?

Answer 45

Long: Used to diagnose secondary adrenal failure​ Short: Used to diagnose primary adrenal failure​

Question 46

What is the gold standard for assessing adrenal reserve?

Answer 46

Insulin tolerance test​ Insulin is administered to achieve hypoglycaemia with glucose less than 2.1 mmol/L​ Hypoglycaemia stimulates the stress response which is mediated by the compensatory hormones for hypoglycaemia​

Question 47

What happens if the insulin tolerance test is contraindicated?

Answer 47

glucagon test can be used​ ​