Hypothyroidism Flashcards Preview

Year 2 Endocrine > Hypothyroidism > Flashcards

Flashcards in Hypothyroidism Deck (34):
1

thyroid hormone synthesis steps

trapping
organification
coupling
storage
secretion

2

what is trapping?

trapping of iodide, transported by NIS

3

organification

- of iodide into iodine and condensed into tyrosine residues
- forms MIT or DIT
- catalyzed by TPO

4

coupling

DIT + MIT = T3
DIT + DIT = T4

5

what is the Jod Basedow effect?

linear increase in organification / T4 formation with increasing iodide concentration

6

what is the wolff-chaikoff effect?

linear decrease in organification / T4 formation with increasing iodide concentration following the jod basedow effect

7

what is the escape phenomenon?

linear increase in organification / T4 formation with increasing iodide concentration following the wolff-chaikoff effect?

8

what is the primary binding protein?

thyroid binding globulin

9

what factors increase TBG?

estrogen (pregnancy, BCP)
congenital

10

what factors decrease TBG?

systemic illness
glucocorticoids

11

besides TSH what other hormone can be increased by TRH?

prolactin

12

which thyroid test is usually the best test of thyroid function? it is inversely proportional to what function?

TSH

inversely proportional to thyroid function

13

hypothryoidism: relationship of TSH and FT4 levels

TSH exceeds the reference range before FT4 gets too low

14

hyperthryoidism: relationship of TSH and FT4 levels

TSH drops below reference range before FT4 gets too high

15

which thyroid test predicts thyroiditis and hypothyroidism?

thyroperoxidase Ab

16

low T3/T4, low TSH

secondary / central hypothyroidism

17

low T3/T4, high TSH

primary hypothyroidism

18

normal T3/T4, low TSH

subclinical hypothyroidism

19

normal T3/T4, high TSH

subclinical hypothyroidism

20

high T3/T4, low TSH

primary hyperthyroidism

21

high T3/T4, high TSH

central hyperthyroidism / resistance

22

secondary / central hypothyroidism

low T3/T4, low TSH

23

primary hypothyroidism

low T3/T4, high TSH

24

subclinical hypothyroidism

normal T3/T4, low TSH

or

normal T3/T4, high TSH

25

primary hyperthyroidism

high T3/T4, low TSH

26

central hyperthyroidism / resistance

high T3/T4, high TSH

27

what is the most common cause of hypothyroidism in iodine-sufficient areas?

hashimoto thyroiditis

28

hashimoto thyroiditis: pathogenesis

autoimmune mediated destruction of thyroid - lymphocytic infiltration

29

what are the clinical features of hashimoto's thyroiditis?

goiter
surface may have a 'bossillated' feel

30

what are the labs associated with hashimoto thyroiditis?

- elevated TSH +/- low T4
- usually TPO antibodies are elevated
- classical heterogeneous appearance on US

31

what is the treatment for hypothyroidism?

levothyroxine (T4)

32

what are the contributing factors to hypothyroidism during pregnancy?

- weight gain
- increasing TBG levels
- increased 5 deiodination

33

what are the clinical features of myxedema coma?

medical emergency consisting of
- mental status changes
- hypothermia
- hypoglycemia
- respiratory failure, hypotension, bradycardia

34

during what condition(s) is TSH no longer reliable? what should be used to guide adjustments?

pituitary or hypothalamic insult

free T4