Thyroid

Question 1

what do colloid cells contain?

Answer 1

tyrosine and thyroglobulin

Question 2

what do parafollicular C cells secrete?

Answer 2

calcitonin

Question 3

explain the synthesis and storage of T3 and T4

Answer 3

1. iodine is taken up by the follicle cells,
2. iodine attached to tyrosine residues on thyroglobulin to form MIT + DIT.
3. Coupling of MIT + DIT = T3 and 2(DIT) = t4
4. stored in colloid

Question 4

is t4 more potent than t3?

Answer 4

no t3 is 4 times more potent than t4

Question 5

where in the body can t4 be converted to t3?

Answer 5

in the liver and kidney

Question 6

what form of thyroid hormone is active? bound or unbound

Answer 6

unbound

Question 7

what is the most abundant plasma protein that thyroxine attaches to?

Answer 7

thyroxine binding globulin (70%)

Question 8

what is the purpose of thyrotrophin (TRH)

Answer 8

comes from the hypothalamus, stimulates TSH from anterior pituitary

Question 9

embryologically where does the thyroid develop from?

Answer 9

invagination of the pharyngeal epithelium, descends from foramen caecum to normal location along the thyroglossal duct

Question 10

what are the embryological abnormalities of thyroid?

Answer 10

failure to descend = lingual thyroid,

excessive descent = retrosternal location and thryoglossal duct cyst

Question 11

biochemically what is happening in hyperthyroidism?

Answer 11

excess T3 and T4

Question 12

85% of hyperthyroidism are due to?

Answer 12

Graves disease

Question 13

what antibodies are seen in Graves disease?

Answer 13

TSH receptor antibodies

Question 14

what are the triad of features in Graves disease?

Answer 14

hyperthyroid, exophthalmos and pretibial myxodema

Question 15

what is the most common cause of hypothyroid?

Answer 15

Hashimoto’s

Question 16

what age range is Hashimotos?

Answer 16

45-60

Question 17

polymorphisms in what genes predispose to Hashimotos?

Answer 17

CTLA-4 and PTPN-22

Question 18

what are the 4 types of thyroid cancer?

Answer 18

papillary, follicular, medullary and anaplastic

Question 19

what is the most common form of thyroid cancer?

Answer 19

papillary carcinoma

Question 20

what is the second most common thyroid cancer?

Answer 20

follicular carcinoma

Question 21

Describe the thyroid cytology system

Answer 21

Thy1 = uninterpretable 
Thy2 = benign 
Thy3 = atypical, probably benign 
thy4= atypical probably malignant 
thy5 = malignant

Question 22

what are the two subtypes of goitre?

Answer 22

diffuse or nodular

Question 23

what are the causes of goitre

Answer 23

iodine deficiency, multi nodular, graves, thyroiditis, tumour, cysts, inherited

Question 24

what would make you think a thyroid nodule was malignant?

Answer 24

below 20 or over 70, male sex, dysphagia/dysphonia, firm hard or immobile lump, lymphadenopathy

Question 25

what is thyroid acropachy?

Answer 25

soft tissue swelling and periostial bone changes

Question 26

what is the thyroid cytology cut off for surgery?

Answer 26

THY3 and above

Question 27

FSH is greater than 30 on two separate occasions what does this indicate?

Answer 27

Peri/menopausal

Question 28

normal thyroid appearance on imaging?

Answer 28

low level uptake, symmetrical

Question 29

Graves disease on imaging?

Answer 29

diffuse uptake, symmetrical

Question 30

Multi nodular goitre on imaging?

Answer 30

asymmetrical, patches of intense uptake and patches missed

Question 31

describe primary hyperthyroidism (biochemically)

Answer 31

TSH is LOW, T3/4 HIGH, overactive thyroid

Question 32

describe primary hypothyroid (biochemically)

Answer 32

TSH is HIGH, t4/3 LOW, failing thyroid

Question 33

why should hypothyroid be restored gradually?

Answer 33

can cause arryhthmias

Question 34

treatment of hypothyroid in younger patients?

Answer 34

50-100 ug/day

Question 35

treatment of hypothyroid in the elderly?

Answer 35

25-50ug.day adjusted every 4 weeks

Question 36

what is the treatment of Hyperthryoidism?

Answer 36

Carbimazole or Propylthiouracil

Question 37

when should TSH be checked after thyroxine therapy begins?

Answer 37

2 months after any dose change, when stable 12-18 months

Question 38

what should the dose of thyroxine be increased by in pregnancy?

Answer 38

25ug

Question 39

what age range is De Quervains?

Answer 39

females 20-50 years

Question 40

describe the changes in T4 in De quervains

Answer 40

High in early stage, low in late and then returns to normal

Question 41

describe the changes in TSH in De Quervains

Answer 41

low in early stage, high in late, then normal