Thyroid Clinical Application

Question 1

What is the initial screening test for suspected thyroid disorders?

Answer 1

TSH test

Question 2

What is the most useful test for hypothyroidism?

Answer 2

Free T4 test

Question 3

What does a total T4 test measure?

Answer 3

Total free T4 and TBG-T4

Question 4

Which is more accurate, free T4 test or a total T4 test?

Answer 4

Free T4 test

Question 5

What is the most useful test for hyperthyroidism?

Answer 5

Total T3 test

Question 6

What does a total T3 test measure?

Answer 6

Total free T3 and TBG-T3

Question 7

Which is more accurate, a free T3 test or a total T3 test?

Answer 7

Total T3 test

Question 8

What is the common order of tests for suspected thyroid disorder?

Answer 8

TSH and free T4 tests ordered together
Total T3 test ordered as needed after

Question 9

What are thyroid antibody tests helpful to diagnose?

Answer 9

Thyroid autoimmune disorders and/or cancer

Question 10

What test is used as a “tumor marker” after a thyroid cancer dx and what does it assess?

Answer 10

Thyroglobulin test
Assesses effects of thyroid cancer treatment

Question 11

What does a T3 Uptake test measure?

Answer 11

Binding capacity of TBG
Indirectly measures amount of plasma TBG

Question 12

High rT3 is associated with?

Answer 12

Acute crisis or severe chronic illness

Question 13

If TSH is high what disorder does that indicate?

Answer 13

Primary Hypothyroidism

Question 14

What happens in early/less severe hypothyroidism?

Answer 14

Thyroid gland doesn’t release enough T3/T4
Liver/kidneys convert T4 into T3 which causes T3 values to remain normal but T4 values decrease
**This is why free T4 test is most useful

Question 15

Why is a free T4 test most useful in early diagnosis of primary hypothyroidism

Answer 15

T3 values may be normal but T4 will be the first value to decrease as hypothyroidism develops

Question 16

What are lab findings for late/progressed hypothyroidism?

Answer 16

T4 shortage means liver/kidneys can no longer convert T4 to T3
T3 values are now also low

Question 17

If TSH is low what disorder does that indicate?

Answer 17

Primary hyperthyroidism

Question 18

What happens in primary hyperthyroidism?

Answer 18

Thyroid releases too much T3/T4

Question 19

Why is a total T3 test most useful in early diagnosis of primary hyperthyroidism?

Answer 19

Liver/kidneys is converting T4 into T3, so T4 levels remain normal but T3 levels increase

Question 20

What are lab findings for late/progressed hyperthyroidism?

Answer 20

T3 and T4 levels are now elevated

Question 21

What are S/S of hyperthyroidism?

Answer 21

Increased CV symptoms (HTN, tachycardia)
Elevated RR
Increased BMs
Hyperactive CNS (tremors, irritable)
Negative effect on diabetes or increased risk of diabetes

Question 22

What disease can cause primary hyperthyroidism?

Answer 22

Grave’s Disease

Question 23

What is Grave’s Disease?

Answer 23

Autoimmune disease that causes excess secretion of T3/T4
Immune systems releases thyroid antibodies that stimulate release of T3/T4

Question 24

What is another cause of primary hyperthyroidism?

Answer 24

Iatrogenic
Too much synthetic thyroxine

Question 25

What are TSH, Free T4, and total T3 values for primary hyperthyroidism?

Answer 25

Decreased TSH Elevated or normal Free T4 Elevated Total T3

Question 26

What lab finding would differentiate between Grave's disease or iatrogenic hyperthyroidism?

Answer 26

If thyroid antibodies are present, it would indicate Grave's over iatrogenic cause

Question 27

What is the difference between primary and secondary hyperthyroidism?

Answer 27

Primary is autoimmune disorder (TSH is decreased) Secondary is due to TSH secreting adenomas (TSH will be elevated and antibodies will not be present)

Question 28

What are the TSH, free T4, and total T3 values for secondary hyperthyroidism?

Answer 28

Elevated TSH Elevated free T4 Elevated total T3

Question 29

What is thyroid storm?

Answer 29

Rare but potentially fatal form of hyperthyroidism

Question 30

What is the hallmark symptom of thyroid storm?

Answer 30

Marked increase in body temperature

Question 31

What triggers thyroid storm?

Answer 31

Acute event (infection, surgery, medications)

Question 32

What is the most common cause of primary hypothyroidism?

Answer 32

Hashimoto's disease (autoimmune disorder)

Question 33

What are other causes of primary hypothyroidism?

Answer 33

Iodide deficiency Thyroidectomy Radiation damage

Question 34

What is myxedema?

Answer 34

Very severe hypothyroidism that can be potentially fatal Sometimes used to describe skin changes seen in hypothyroidism

Question 35

What can hypothyroidism cause?

Answer 35

Cretinism (impaired congenital development) Gross Dwarfism Cognitive impairment

Question 36

What are the TSH, free T4, and total T3 findings of Primary Hypothyroidism?

Answer 36

Elevated TSH Decreased free T4 Decreased total T3

Question 37

What lab finding would indicate Hashimoto's over other causes of hypothyroidism?

Answer 37

Presence of thyroid antibodies

Question 38

What is the difference between primary and secondary hypothyroidism?

Answer 38

Primary has elevated TSH Secondary has decreased TSH

Question 39

What causes secondary hypothyroidism?

Answer 39

Pituitary gland pathology/ Hypopituitarism

Question 40

What are other lab findings of Secondary Hypothyroidism?

Answer 40

Decreased levels of other pituitary hormones (GH, FSH, LH, ADH, ACTH, prolactin)

Question 41

What causes goiter to form in Grave's disease?

Answer 41

Increased thyroglobulin and T3/T4 are stored in the colloid

Question 42

What causes goiter to form in Hashimoto's disease and iodide deficiency?

Answer 42

Increased thyroglobulin stored in colloid