Hormone Measurement and Interpretation

Question 1

What is the normal range of free thyroxine?

Answer 1

9-25 pmol/L

Question 2

What is the normal range of TSH?

Answer 2

0.4-4.7 mIU/L

Question 3

What is wrong if there is low thyroxine but high TSH?

Answer 3

thyroid is under active

Question 4

What is wrong if there is low thyroxine and low TSH?

Answer 4

pituitary is under active

Question 5

What is wrong if there is high thyroxine and low TSH?

Answer 5

thyroid is over active

Question 6

Why is TSH a better test than free thyroxine?

Answer 6

changes in TSH occur a lot earlier than thyroxine

Question 7

Describe the glucose tolerance test

Answer 7

patient is given an overload of glucose and their glucose is measured over 2 hours - if at 2 hours their glucose is over 11mmol/L this is defined as diabetes

Question 8

Describe the dexamethasone suppression test

Answer 8

patient takes dexamethasone which should suppress the pituitary so therefore should see a drop in cortisol - if the cortisol is still high this may indicate Cushing’s syndrome

Question 9

Describe the synacthen stimulation test

Answer 9

patient takes synacthen (synthetic ACTH) and then cortisol levels are measured - if the cortisol doesnt rise this may indicate adrenal failure

Question 10

Describe the combined pituitary function test

Answer 10

the patient is given insulin which is a physiological stressor - expect to see a rise in ACTH and cortisol - the patient is also given TRH so expect to see a rise in TSH and prolactin and the patient is given LRHR so expect to see a rise in LH and FSH

Question 11

Describe the growth hormone stimulation test

Answer 11

stimulate by exercise and measure GH

Question 12

Describe the growth hormone suppression test

Answer 12

give patient glucose and measure GH (which should be suppressed by glucose)

Question 13

What are the two types of immunoassays used to measure hormone levels?

Answer 13

competitive and non competitive

Question 14

Describe a competitive immunoassay

Answer 14

there is a limited amount of antibody for the hormone attached to the test tube - the serum containing the hormone is added as well as a labelled hormone - there is competition between labelled and natural because there is limited antibody - a high signal means a lower hormone concentration

Question 15

Describe a non competitive immunoassay

Answer 15

two different antibodies are used - one is stuck to the test tube and the other is labelled - there is an excess of antibodies - the serum with the hormone is added and all of the hormone will bind to the antibodies then the second antibody will bind - measure the signal - a high signal means a high hormone concentration