Thyroid tests

Question 1

Thyrotropin is testing for

Answer 1

TSH

Question 2

thyroid diagnostic options

Answer 2

• US
• radioiodine uptake and scan
• fine needle aspriation biopsy

Question 3

Thyrotopin = TSH is tighly regulated by serum levels of

Answer 3

T4 and T3: negative feedback loop

Question 4

the majority of T4 is free or bound? Which is more relevant

Answer 4

• A small fraction circulates as free T4
  
  • only free hormone is biologically active

Question 5

T4 is converted to T3 where

Answer 5

• thyroid
• liver (primarily)

Question 6

What is endogenous hyperthyroidism

Answer 6

• overproduction of thyroid hormone

Question 7

which conditions falls under endogenous hyperthyroidism

Answer 7

• graves disease
• toxic multinodular goiter
• toxic adenoma
• thyroiditis

Question 8

List the thyroid antibodies

Answer 8

1. thyroid peroxidase antibodies (TPO)
2. TSH receptor antibodies (TRAb)
3. Thyroglobulin antibodies (Tg)

Question 9

Thyroid peroxidase antibodies (TPO) is most sensitiev for

Answer 9

• autoimmune thyroid disease
  
  • identifies 95% hashimotos
  • identifies 85% of graves

Question 10

TSH receptor antibodies (TRAb) and thyroid-stimulating antibody (TSAb) are present in 90% of patients with

Answer 10

Graves disease

Question 11

Thyroglobulin antibodies indicate

Answer 11

• inflammation or destruction of gland
• seen in hyper- and hypothyroidism and autoimmune disorders

Question 12

Radioiodine uptake and scan is used to evaluate for

Answer 12

• Hyperthryoidism
  
  • graves
  • toxic nodular goiter
  • thyroid nodule

Question 13

Radioiodine uptake and scan reflects what

Answer 13

iodine metabolism of gland

Question 14

Radioiodine uptake and scan contraindicated in

Answer 14

• pregnancy
• breastfeeding

Question 15

Radioiodine uptake and scan: High uptake indicates

Answer 15

excessive synthesis

Question 16

Radioiodine uptake and scan: Low uptake indicates either

Answer 16

1. inflammation/destruction of thyroid tissue with release of preformed hormone into circulation
2. extrathyroidal source of thyroid hormone

Question 17

How will graves disease and nodules/TMG differ on Radioiodine uptake and scan

Answer 17

• Graves: homogenous uptake
• nodules or TMG: irregular uptake

Question 18

do hyperfunctioning “hot” nodules need to be biopsied?

Answer 18

• no
• they are rarely malignant

Question 19

What values would you expect in graves disease

• TSH
• FT4
• T3
• RAI uptake/scan

Answer 19

• TSH low
• FT4 and T3 elevated
• RAI: homogenous, increased uptake

Question 20

What is the most common cause of primary hypothyroidism

Answer 20

hashimoto thyroiditis

Question 21

Central hypothyroidism can be either secondary or tertiary. where is the problem

Answer 21

• secondary: pituitary
• tertiary: hypothalamus

Question 22

in central hypothyroidism, what do you expect TSH, T4 and T3 levels to be

Answer 22

ALL LOW

Question 23

iatrogenic hypothyroidism is caused by

Answer 23

• tx with radioactive iodine
• medications
  
  • lithium
  • amiodarone
  • iodinated contrast agents

Question 24

risk of thyroid CA higher in

Answer 24

• children
• adults < 30 or > 60
• h/o head and neck irradiation
• fhx of thyroid CA

Question 25

If thyroid nodules are hypofunctioning, or “cold” are they more likely to be malignant?

Answer 25

yes

Question 26

List steps of evaluation for thyroid nodules

Answer 26

1. order TSH
   
   1. low -> order thyroid uptake and scan
      
      1. hot nodule -> likely benign
         
         • check FT4, if high, treat hyperthyroidism
      2. cold nodule -> consider FNA biopsy
   2. normal or elevated
      
      1. consider FNA biopsy
      2. check for TPO antibodies
         
         1. if high -> hashimoto thyroiditis

Question 27

TPO antibodies are elevated in what condition

Answer 27

Hashimoto thyroiditis

Question 28

What percentage of hot and cold nodules are benign

Answer 28

• hot nodule: almost always benign
• cold nodule: 90-95% benign; 5-10% malignant

Question 29

What is the most sensitive test for evaluating thyroid nodules

Answer 29

thyroid US

Question 30

What is the single most accurate, reliable, cost effective test to diagnose thyroid CA

Answer 30

fine needle aspiration biopsy (FNA)