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MD1 Endocrine > Hormone Measurement and Interpretation > Flashcards

Hormone Measurement and Interpretation Flashcards

1
Q

Why measure hormones?

A 
Confirm clinical suspicion
Diagnose sub-clinical problems
Assess treatment
Time procedures
Screening
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2
Q

What are the approaches to measuring hormones?

A

Measure trophic hormone
Measure actual hormone
Measure both trophic and actual hormone

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3
Q

How big a change in free T4 leads to a large change in TSH?

A

Small change

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4
Q

Can a test result outside the reference range still be normal?

A

Yes

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5
Q

What can a hormone level test result vary with?

A 
Age
Sex
Race
Nutritional state
Menstrual state
Medication
Person
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6
Q

Is what is “normal” for a population the ideal?

A

Not always, eg: cholesterol

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7
Q

What are the thyroid function tests with an overactive thyroid?

A

Decreased TSH

Increased T4

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8
Q

What are the thyroid function tests with an underactive thyroid?

A

Increased TSH

Decreased T4

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9
Q

What are the thyroid function tests with pituitary underactivity?

A

Decreased TSH

Decreased T4

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10
Q

What are the thyroid function tests in subclinical hypothyroidism?

A

Normal T4

Elevated TSH

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11
Q

How long can TSH take to return to normal after treatment starts in hypothyroidism?

A

4-6 weeks

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12
Q

How long can TSH and T4 take to return to normal after treatment starts in hyperthyroidism?

A

T4 decreases relatively quickly

TSH increases relatively slowly

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13
Q

What factors affect the tests used?

A 
Normal homeostasis
Common causes of dysfunction
Availability of test
Reliability of test
Sensitivity, specificity
Cost
Government regulation
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14
Q

What is dynamic testing of hormones?

A

Sampling at multiple time points

Can involve stimulating/suppressing gland > see if responds appropriately

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15
Q

Why is dynamic testing used in subclinical disease?

A

Diseased system may appear to function normally under basal conditions but show abnormalities if stressed

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16
Q

Why is dynamic testing used to investigate abnormal results?

A

Is abnormal hormone result due to physiological or pathological cause?

17
Q

How do you test glucose tolerance?

A

Fasting patient
75 g glucose orally at 0 min
Specimens for glucose take at 0, 1, and 2 hrs

18
Q

What is the effect of dexamethasone?

A

Strong glucocorticoid > suppresses ACTH > decreasees adrenal stimulation

19
Q

How do you do a dexamethason suppression test?

A

Patient takes dexamethasone at midnight

Measure cortisol before and after dexamethasone

20
Q

How do you do a synacthen stimulation test?

A

Stimulate gland with synacthen (ACTH) > measure cortisol levels
Give synacthen intramuscularly at 0 min
Blood cortisol at 0, 30, and 60 min

21
Q

How is a combined pituitary function test conducted?

A

Give insulin, TRH, LHRH at time 0 min

Performed under medical supervision because of chance of hypoglycaemia

22
Q

How is growth hormone release stimulated in a growth hormone stimulation test?

A

Exercise
Hypoglycaemia
Arginine

23
Q

How is growth hormone release suppressed in a growth hormone suppression test?

A

Elevated glucose

24
Q

How are hormones usually measured?

A

Immunoassays

25
Q

What are the types of immunoassays?

A

Competitive

Non-competitive (sandwich)

26
Q

What are the principles of competitive immunoassays?

A

Competition between specimen hormone and added label hormone for limited amount of Ab
Increased natural hormone binding > decreased fluorescent signal

27
Q

What are the steps in a competitive immunoassay?

A
  1. Add serum and labelled hormone to Ab
  2. Incubate
  3. Remove non-bound labelled hormone
  4. Measure amount of label
28
Q

What are the principles of sandwich immunoassays?

A

Ag held between 2 Abs, one of which labelled

Improved specificity as 2 binding sites used

29
Q

What are the steps in a sandwich immunoassay?

A
  1. Add serum to Ab
  2. Add labelled Ab
  3. Incubate
  4. Remove non-bound labelled Ab
  5. Measure amount of signal
30
Q

What are some problems with measuring hormones?

A

Different results from different labs because of different uses of standards
Poor quality of sample
Potential Ab interference

31
Q

Which antibodies can interfere with immunoassays?

A

T3/T4 autoantibodies
Heterophile Abs
Human anti-mouse Abs
Rheumatoid factor

32
Q

How is hormone measurement affected when a patient has hormone autoantibody?

A

Rare
Differing effects depending on type of assay and how Ab binds
AutoAb binds to naturally occurring hormone

33
Q

How is hormone measurement affected when a patient has heterophilic antibody?

A

Falsely high results because links reaction Abs

MD1 Endocrine (18 decks)

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