Principles of endocrine disease and its assessment Flashcards

1
Q

Where do peptide hormones act and why?

A

→ surface receptors because they are charged

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2
Q

Where do steroid hormones act and why?

A

→ nuclear receptors because they are aliphatic

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3
Q

What type of hormone is thyroid hormones?

A

→ steroid

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4
Q

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

A

→ dynamic

→ Hormones are pulsatile and vary during the day

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5
Q

How do you do a radioimmunoassay in the lab?

A

→ 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

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6
Q

What is an advantage of a total hormone assay?

A

→ cheap

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7
Q

What are 2 disadvantages of a total hormone assay?

A

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

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8
Q

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

A

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

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9
Q

What are advantages of a free hormone assay?

A

→ Representative of active hormone fraction

→ Not binding protein dependant

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10
Q

What are disadvantages of a free hormone assay?

A

→ Complex and expensive

→ Can have poor reproducibility

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11
Q

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

A

→ decreases the accuracy

→ transfer errors

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12
Q

How do you separate free hormones in an assay?

A

→ dialysis membrane

→ causing binding protein to precipitate out

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13
Q

What does the radiometric assay work on?

A

→ on peptide hormones

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14
Q

Why is measuring a peptide hormone difficult?

A

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

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15
Q

How does a radiometric assay work?

A

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

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16
Q

How does tri iodothyronine get produced?

A

→ 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

17
Q

How do you measure overproduction of thyroid hormone?

A

→ autoantibodies
→ Technetium scanning
→ Thyroid function

18
Q

How do you measure underproduction of thyroid hormone?

A

→ Thyroid function

→ Autoantibodies

19
Q

How do you check for thyroiditis?

A

→ Thyroid function
→ ESR
→ Technetium

20
Q

Why is thyroiditis sometimes mistaken for overproduction of thyroid hormone?

A

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

21
Q

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

A

→ Ultrasound

→ Fine needle aspiration biopsy

22
Q

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

A

→ 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

23
Q

What is the negative feedback mechanism of thyroxine?

A

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

24
Q

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

A

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

25
If TSH is high and T3 and T4 are low what is the diagnosis?
→ Hypothyroidism →Less negative feedback → TSH should increase → Primary because TSH is high - correct brain function
26
If TSH is low and T3 and T4 are low what is the diagnosis?
→ Hypothyroidism → TSH should increase → brain function incorrect → Secondary
27
If T4 is low, TSH is low and T3 is normal what is the diagnosis?
→ Sick Euthyroid
28
How should the dexamethasone suppression test be in normal people?
→ Cortisol level should decrease below 50 | → high dose should be 50% of baseline
29
Dethamethasone test in people with cushings disease?
→ low dose = not below 50 →high dose = more than 50% decrease → ACTH are high
30
Dexamethasone test in people with adrenal tumor?
→ low dose = not below 50 → high dose = less than 50% decrease → ACTH is low
31
Dexamethasone test in people with ectopic ACTH?
→ low dose = more than 50 → high dose = less than 50 decrease → ACTH very high
32
How do you test for Addisons?
→give synthetic ACTH | → Cortisol level rises
33
What is the short synacthen test?
→ Shot of ACTH → Cortisol goes above 400 → Diagnose adrenal failure
34
What is the long synacthen test used for?
→Blood taken over 24 hours | → Diagnose secondary adrenal failure
35
What happens in the long synacthen test if it is pituitary vs Addisons?
→ Cortisol levels rise → can cause growth of adrenal gland → if addisons the cortisol wouldn't be raised
36
What is done to test for growth hormone deficiency?
→ Large insulin dose → hypoglycaemia (less than 2.1) → cortisol should increase
37
What is the oral glucose tolerance test?
``` → test for GH excess → 75g oral glucose → samples for GH taken → normal individuals GH fall → Acromegaly = rise ```
38
If the hormone is too high how do you test?
→ Suppress it
39
If the hormone is too low how do you test for it?
→ Stimulate it