Endocrinology- thyroid gland

Question 1

Where is thryoid gland located and what nerve runs close to it?

Answer 1

BELOW thyroid cartilage

Question 2

Label histopthology of a throid lobe?

Answer 2

Follicle -follicular cells, colloid

PARA(next to) follicular cells

Question 3

Development of throid gland (beginning in tongue) from embryo until adult?

Answer 3

outpouching from floor of pharynx (base of tongue)

develops to thyroglossal duuct

then develop to 2 lobes

duct dissapear leaving leaving foramen caecum

Final position week 7 then thryoid gland develops

Question 4

How does thyroid gland function in follicular cell (when TSH arrive from pit gland)?

Answer 4

TSH bind to TSH receptor on follicular cells.

stimulated: -production + release of thyroglobin into colloid

• also transport of I- from blood through cell to colloid
• production of enz TPO (cataylse both iodniation rxn with H202)

Question 5

What happens to thyroglobin after in the colloid?

Answer 5

First iodide is oxides to iodine.

Binds to TG form MIT & DIT chains (that are still on TG)

then coupling reaction to form T3 and T4 chains (that are still on TG)

These are cleaved from thyroglobulin in the follicular cell cytoplasm (lysosomal enzymes) to yield T4 and T3

ENTER blood

Question 6

on a molecular level of thyroglobin how does this occur?

Answer 6

TG (long peptide chain) has many Tyrosine (AA) residues x100

Tyrosine can be iodinated.

1 iodonation- MIT 2 iodonation- DIT

combine MITs and DITs (copling rxn)

PRODUCE- T3 and T4

Question 7

What does this visually look like?

Answer 7

Question 8

T3 is active but most thyroid hormones produced is T4 (inactive) how is this resolved?

Answer 8

In targeted tissues T4 is deiodinated to T3 by DEIONDINASE enz

Question 9

What happens if you deiodinate in a different position?

Answer 9

Produce an inactive form of T3

Question 10

How is it transported in blood ( 3 attached ways)?

Answer 10

1- 80% by TBG

2-Albumin

3-prealumin (transthyretin)

v little unbound

Question 11

How does it have affect on gene expression?

Answer 11

enter nucleus + alter gene expression activ gene transciption

Question 12

What is it overall purpose?

Answer 12

Essential for growth, development esp brain

disease if low in baby crentinism

tested in baby-heel prick measure TSH

Question 13

What is T3/4 affects on systems and body?

Answer 13

increase BMR, increase metabolism, increasde cardiac output, maturation CNS, Catecholamines( hormones adrenal glands)

Question 14

How is T3/4 production regulated?

Answer 14

T3/4 negative feedback to hypothalamus and anterior pituarity.

as well as high iodide prev production T3/4

Question 15

Why are women suspectible to thyroid disease

Answer 15

Majority of T disease due to autoimmunity, antiobodies against T gland.

women more antibodies, more antibody variance due to giving birth.

Question 16

What happens to blood levels in hypothyroidism (auto damage to cells)?

Answer 16

Thyroxine (T4) levels decline.

TSH levels increase due to negative feedback

Question 17

Common disease associated of hypothyroidism?

Answer 17

Hashimoto’s thryoditis

immune attack T gland + inflammation leads to hypo

Question 18

How is hypothyroidism diagnosed

Answer 18

enlarged thyroid glands

elevated thyroid stimulating hormone (TSH)

low thyroid hormone (Free thyroxine [Free T4]) levels

TPO antibody elevated

Question 19

Symptoms of hypothyrodism?

Answer 19

Paresthesia hypo cause fluid retention resulting in swollen tissues that exert pressure on peripheral nerves.

shaggy hair + hair loss

fatigue+ memory lost

swollen gace

enlarged T gland due to inflammation

slower HR- bradycardia

Weight gain

rough skin

deepening voice

cold intolerance

Question 20

What treatment usually given to hypothyroidism?

What is it?

Answer 20

Levothyroxine (T4)

Question 21

How is that drug dosed?

Answer 21

adjust TSH to normal as usually too high

administered orally

Question 22

When else can Levothyroxine be used?

Answer 22

For HYPERthyrodism- blocking and replacement regimen

1. use iodine leads to T gland to underactive, prevent all T3/4
2. Give levo for functioning in body

Question 23

What are other alternatives?

Answer 23

Liothyronine (T3)

Has same effect but more expensive

Question 24

Why is problem with combined T3/4 treatment?

Answer 24

Switch of hypothalamus cells as seeing much of T3/4 so supress TSH + toxicity

Question 25

What levels changes are there in hyperthyoridism?

Answer 25

Thyroxine levels increase

TSH decrease

Question 26

Examples of disease causing hyperthryoidism?

Answer 26

Graves disease- gland is enlarged

Toxic mutlinodular goitre- multiple nodules (fluid sacs) autonomically functioning

solitary toxic nodule (singular node)

Question 27

what is pathophysiology of graves disease?

What does it look like?

Answer 27

Antibodies bind to and stimulate TSH receptor.

Looks smooth, enlarged and neck is fat (GOIRTE)

Question 28

What are other symptoms of Graves disease?

Answer 28

Other antibodies bind to other places

(muscles beind eye lead to) Exopthalamos- buldging eye out of orbit

(soft tissue of shins) Pretibial myxoedema - ‘orange peal’

Question 29

Symptoms of hyperthyroidism?

Answer 29

heat intolerance

weight loss

myopathy-muscle weakness

nervousness, insomia, depression

enlarged thyroid glands

increase HR

high BP

moist skin

irregular menstral cycle