L6 (L7 by uni) - thyroid

Question 1

what is thyroid gland

Answer 1

secretes thyroid hormones (THs) into the blood directly

-

Question 2

2 main THs

Answer 2

T3 and T 4

Question 3

what is hyperthryoidism

Answer 3

too much of TH s

Question 4

what is hypothyoridism

Answer 4

-too little of THs

Question 5

diseases relating to thyroid

Answer 5

hyper and hypothyroidism

, goiture,(swelling) and cancer

Question 6

where is thryoid gland located

Answer 6

in the neck

-has 2 lobes

Question 7

cell types present in the thyroid gland

Answer 7

C cells

follucular epithelial cells

Question 8

what is c cells

Answer 8

involved in Ca homeostasis

Question 9

how does C cell regulates Ca leve,s

Answer 9

secretes caicitonin in response to Ca levels

- inhibits osteoblasts from reabsorbing Ca

Question 10

general structure of TH

Answer 10

has iodine atoms - essential for TH biosynthesis

Question 11

how is iodine taken up in to the follicullar cells then into lumen

Answer 11

by NIS ( Na - I co transporter ) on basolateral membrane 
- then through pendrin on the apical membrane into the lumen

Question 12

what is the most highly expressed proteins in the thyroid

Answer 12

thyroglobulin (Tg)

• large glycoproteins
• helps in the TH hormone synthesis and storage

Question 13

what is thyroid peroxidase

Answer 13

TPO

- an enzyme involved in oxidation of iodine and conjugation of the iodotyrosines to form THs

Question 14

where is iodinated Tg stored

Answer 14

in the follicular lumens as colloid

Question 15

process of TH’s release

Answer 15

iodo Tg endocytosed from the lumen into the epithelial cell as vesicles

• the Tg degraded to form T3 and T4
• the T3 and T4 transported into the blood by MCT8 transporter on the basolateral membranr

Question 16

what is the releasing factor for stimulating TSH from PG

Answer 16

TRH from hypothal

Question 17

how does the TSH activate the stimulation of production of TH s

Answer 17

binds to TSHReceptor on the thyroid cell-

• causes the G protein GDP to convert into GTP
• GTP activates the signalling cascade which ends in activated PKA

Question 18

what does the activated PKA do in the TH production

Answer 18

activates the CREB - which induces gene transcription

Question 19

types of carrier proteins bound to THs

Answer 19

• thyroxine binding globulin (TBG)
• transthyretin (TTR)b
• albumin

Question 20

what type of inactive hormone is T4

Answer 20

prohormone - gets converted into T3 which is active hormone

Question 21

what can regulates the T3 levels

Answer 21

transporters - taking in T3
deiodinases - enzymes removing Iodine
- thyroid hormone receptors

Question 22

types of deiodinases and their function

Answer 22

D1 - can remove iodine from outer and inner rings

D2 - can remove iodine from outer - forms active T3

D3 - can remove iodine inner rings - forms inactive T3

Question 23

roles of TH

Answer 23

development, regulation of growth and control of basal metabolic rate (BMR)

Question 24

what happens when there is lack of THs

Answer 24

• can become mentally deficient, ivversibely motor and cognitive impairment

Question 25

what is BMR

Answer 25

min energy required for basic function

Question 26

effect of TH on BMR

Answer 26

increases it through O2 consumption and heat production

Question 27

metabolic effects of Ths

Answer 27

increase glucose production

• increase fat metab
• decrease plama cholestral

Question 28

what receptors does TH like T3 bind to induce gene expression in a target cell

Answer 28

nuclear hormone receptors containing thyroid hormone response elements (TREs)