Hormone Measurement and Interpretation Flashcards Preview

MD1 Endocrine > Hormone Measurement and Interpretation > Flashcards

Flashcards in Hormone Measurement and Interpretation Deck (33):
1

Why measure hormones?

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

2

What are the approaches to measuring hormones?

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

3

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

Small change

4

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

Yes

5

What can a hormone level test result vary with?

Age
Sex
Race
Nutritional state
Menstrual state
Medication
Person

6

Is what is "normal" for a population the ideal?

Not always, eg: cholesterol

7

What are the thyroid function tests with an overactive thyroid?

Decreased TSH
Increased T4

8

What are the thyroid function tests with an underactive thyroid?

Increased TSH
Decreased T4

9

What are the thyroid function tests with pituitary underactivity?

Decreased TSH
Decreased T4

10

What are the thyroid function tests in subclinical hypothyroidism?

Normal T4
Elevated TSH

11

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

4-6 weeks

12

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

T4 decreases relatively quickly
TSH increases relatively slowly

13

What factors affect the tests used?

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

14

What is dynamic testing of hormones?

Sampling at multiple time points
Can involve stimulating/suppressing gland > see if responds appropriately

15

Why is dynamic testing used in subclinical disease?

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

16

Why is dynamic testing used to investigate abnormal results?

Is abnormal hormone result due to physiological or pathological cause?

17

How do you test glucose tolerance?

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

18

What is the effect of dexamethasone?

Strong glucocorticoid > suppresses ACTH > decreasees adrenal stimulation

19

How do you do a dexamethason suppression test?

Patient takes dexamethasone at midnight
Measure cortisol before and after dexamethasone

20

How do you do a synacthen stimulation test?

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

21

How is a combined pituitary function test conducted?

Give insulin, TRH, LHRH at time 0 min
Performed under medical supervision because of chance of hypoglycaemia

22

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

Exercise
Hypoglycaemia
Arginine

23

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

Elevated glucose

24

How are hormones usually measured?

Immunoassays

25

What are the types of immunoassays?

Competitive
Non-competitive (sandwich)

26

What are the principles of competitive immunoassays?

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

27

What are the steps in a competitive immunoassay?

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

28

What are the principles of sandwich immunoassays?

Ag held between 2 Abs, one of which labelled
Improved specificity as 2 binding sites used

29

What are the steps in a sandwich immunoassay?

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

30

What are some problems with measuring hormones?

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

31

Which antibodies can interfere with immunoassays?

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

32

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

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

33

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

Falsely high results because links reaction Abs