Lec 7 - Thyroid Gland

Question 1

thyroid gland structure

Answer 1

2 lobes
(20-30% of pop have a 3rd lobe = pyrimidal lobe)

Question 2

which cells secrete calcitonin

Answer 2

parafollicular c cells

Question 3

what is thyroid follicle filled with

Answer 3

thyroglobulin filled

Question 4

why is thyroid follicle described as dynamic

Answer 4

both shape and size epithelial cells and amount of thyroglobulin changes

Question 4

what does hypothalamus release to trigger thryoid stimulating hromone

Answer 4

thyrotropin releasing hormone
TRH

Question 5

where is TSH released from

Answer 5

APG

Question 6

what does TSH do

Answer 6

acts on thyroid gland = thyroid hromones released

Question 7

what negatively feedbacks of APG and hypothalamus

Answer 7

T3

Question 8

what effects TRH release from hypothalamus

Answer 8

• diurnal release
• stresses decrease release

Question 9

what type of hormone is thyroid stim hormone

Answer 9

glycoprotein hormone
(the one with the differing beta subunit)

Question 10

what determines the stability and biological activity of TSH

Answer 10

CHO side chains

Question 11

what cells produce TSH

Answer 11

pituitary thyrotrophs

Question 12

how do thyrotrophs increase TSH production

Answer 12

by increasing the production of alpha and beta subunits needed to make it

Question 13

how does high TSH affect thyroid follicle

Answer 13

• inc tg loss from lumen into cells
• inc blood flow
• inc pseudopodia
• cuboid to columnar

Question 14

how does iodide get into thyroid follicular lumen

Answer 14

passes through 2 membranes
basolateral and apical through the follicular cells

Question 15

2 transporters for I- in basolateral cell membrane

Answer 15

• Na+/K+ ATPase (increases Na+ on outside)
• sodium iodide symporter (NIS)
  (brings iodide back in with Na+)

Question 16

transporter for iodide in apical cell membrane

Answer 16

pendrin

Question 17

what enzyme complex iodinates thyroglobulin

Answer 17

thyroid peroxidase (TPO)
= oxidises iodide so it can connect with Tg

Question 18

what complex is made when plenty of iodide

Answer 18

di-iodotyrosine (DIT)
2 of these make T4

Question 19

what complex is made when less iodide

Answer 19

monoioidotyrosine
1 of these and a DIT make T3

Question 20

normal proportion of T4 to T3

Answer 20

90% T4
10% T3

Question 21

T4 other name

Answer 21

thyroxine

Question 22

T3 other name

Answer 22

tri-iodothyronine

Question 23

what pathway does TSH use

Answer 23

• adenylate cyclase = cyclic AMP = protein kinase A

Question 24

iodine deficiency effect

Answer 24

= derbyshire neck
non-toxic GOITRE
- effect of thyroid gland trying to extract iodine from blood
- lack of iodide means less T3 produced = NO NEGATIVE FEEDBACK to stop TSH

Question 25

What is thyroid gland lobes connected by

Answer 25

isthmus