Thyroid Physiology & Pathology

Question 1

what is the thyroid composed of?

Answer 1

follicles

Question 2

colloid

Answer 2

tyrosine containing thyroglobulin filled spheres enclosed by follicular cells

Question 3

parafollicular C cells

Answer 3

secrete calcitonin

Question 4

T4

Answer 4

thyroxine

Question 5

T3

Answer 5

triiodothyronine

major biologically active thyroid hormone

Question 6

which is more potent, T3 or T4?

Answer 6

T3

Question 7

how is T3 created?

Answer 7

T4 converted to T3 by liver & kidney

Question 8

what makes T3 & T4 able to bind plasma proteins?

Answer 8

hydrophobic/lipophillic

Question 9

is the bound or unbound form of T3 & T4 biologically active?

Answer 9

unbound

Question 10

what do thyroid hormones do to basal metabolic rate?

Answer 10

increase

Question 11

what do thyroid hormones do to thermogenesis?

Answer 11

increase

Question 12

what do thyroid hormones do to blood glucose?

Answer 12

increase due to stimulation of glycogenolysis & gluconeogenesis

Question 13

what do thyroid hormones do to insulin dependent glucose uptake into cells?

Answer 13

increase

Question 14

what do thyroid hormones do to lipid metabolism?

Answer 14

mobilise fats from adipose tissue & increase fatty acid oxidation in tissues

Question 15

what do thyroid hormones do to protein synthesis?

Answer 15

increase

Question 16

the production & secretion of which hormone requires thyroid hormones?

Answer 16

growth hormone releasing hormone

glucocorticoid-induced GHRH release

Question 17

which hormones require the presence of thyroid hormone for activity?

Answer 17

GH/somatomedins

Question 18

how do thyroid hormones affect the development of foetal & neonatal brain?

Answer 18

myelinogenesis & axonal growth require thyroid hormones

Question 19

what does stress do to TRH & TSH?

Answer 19

inhibits their release

Question 20

what rhythm of secretion do thyroid hormones exhibit?

Answer 20

circadian

Question 21

what does exposure to cold environments do to TRH release?

Answer 21

stimulates it

Question 22

what does TRH release stimulate?

Answer 22

TSH release

Question 23

what does TSH release increase?

Answer 23

T3 & T4 release from thyroid

Question 24

what can primary deficiency of thyroid hormones be associated with?

Answer 24

enlarged thyroid

Question 25

wat can secondary deficiency of thyroid hormones be due to?

Answer 25

TRH or TSH

Question 26

what is the other cause of deficiency of thyroid hormones?

Answer 26

lack of iodine in diet

Question 27

what is grave's disease?

Answer 27

autoimmune hyperthyroidism

Question 28

what symptoms are common in Grave's disease?

Answer 28

exopthalmos | goitre

Question 29

what is each follicle in the thyroid gland surrounded by?

Answer 29

flat to cuboidal follicular epithelial cells

Question 30

what's at the centre of each follicle?

Answer 30

dense amorphsc pink material containing thyroglobulin

Question 31

C cells

Answer 31

parafollicular cells

Question 32

how are C cells arranged in the thyroid?

Answer 32

occasionally scattered

Question 33

what do C cells look like?

Answer 33

slightly larger cells with clearer cytoplasm

Question 34

what do the symptoms of hyperthyroidism occur as a result of?

Answer 34

excess of T3 & T4

Question 35

what's the most common cause of hyperthyroidism?

Answer 35

Grave's disease

Question 36

what are the other causes of hyperthyroidism excluding Grave's disease?

Answer 36

hyperfunctioning nodules tumours thyroiditis

Question 37

what are the triad of features of Grave's disease?

Answer 37

Hyperthyroidism with diffuse enlargement of the thyroid Eye changes (exophthalmos) Pretibial myxoedema.

Question 38

what do the eye changes in Grave's disease result from?

Answer 38

fibroblasts etc expressing TSH receptors

Question 39

what are the symptoms & signs of hypothyroidism dir to?

Answer 39

low levels of T3 & T4

Question 40

what are the majority of cases of hypothyroidism due to?

Answer 40

hashimoto's thyroiditis

Question 41

what is hashimoto's thyroiditis?

Answer 41

gradual failure of thyroid function due to auto-immune destruction of thyroid tissue

Question 42

what may hashimoto's thyroiditis be preceded by?

Answer 42

transient hyperfunction (hashitoxicosis)

Question 43

goitre

Answer 43

any enlargement of the thyroid gland

Question 44

adenomas

Answer 44

Discrete solitary mass Encapsulated by a surrounding collagen cuff Composed of neoplastic thyroid follicles