thyroid hormones asynch-pharm

pharm 2

thyroid is located

in from of the esophagus

the thyroid gland is the. . .

largest endocrine glands

the thyroid controls

how quickly the body uses energy, makes proteins, controls how sensitive the body is to other hormones

the primary function of the thyroid is the

production of hormones T3, T4, and calcitonin

hypothalamus

regulates the anterior pituitary gland by releasing TRH

TRH

thyroid releasing hormone

TSH

thyroid stimulating hormone

anterior pituitary

regulates the thyroid gland by releasing TSH

they thyroid gland releases

T3 and T4

T3 and T4 normally

do negative feedback by acting on the hypothalamus

if someone has hypothyroidism, their TSH will be

high in the blood tests

if someone has hyperthyroidism, their TSH will be

low in the blood tests

steps of how T3 and T4 get released

1. the hypothalamus releases TRH

2. the TRH travels thru the portal venous system to get to the anterior pituitary

3. the anterior pituitary then releases TSH and it gets into the blood

4. TSH act on the thyroid gland

5. the thyroid then releases T3 and T4

6. T3 and T4 will travel back to the hypothalamus and will do negative feedback (in a normally functioning body)

iodine

is important for they thyroid gland→ needs iodine in order to produce a proper amount of thyroid hormone

if iodine is too low. . .

then the proper amount if thyroid hormone cannot be made

where are thyroid hormones produced?

within thyroid follicles that make up the thyroid gland

T4 is . . .

the precursor to T3

T3

triiodothyronine

T4

tetraiodothyronine

T3 is. . .

4 times more potent (so our bodies do not produce much of it)

T4 is produced

90% of the time

it is less potent and acts as a safeguard mechanism to decreased production of T3

they thyroid follicles are the. . .

main powerhouse of the thyroid gland

thyroid follicle structure

colloid of the the follicle

the center

where thyroid hormone (both precursors) are being produced

capillaries

where blood/amount of iodine comes in

capillaries face the

basolateral membrane of each cell

basolateral membrane

the outside of the follicle

apical membrane

faces the lumen

where do we get most of our iodine?

from iodized table salt (NaCl)

foods with the most iodine

1. dried seaweed

2. cod fish

3. cranberries

4. yogurt

5. baked potatoes

6. turkey breast

7. navy beans

8. tuna

9. strawberries

10. eggs

thyroid peroxidase

oxidized iodine

pendrin

a transporter that take iodine all the way across the cell/follicle and into the lumen

iodination

the process of how the thyroid hormone precursor and the iodine get together→ how they integrate→ how they combine

conjugation

losing H→ rings together

how the precursor hormone either gets 3 or 4 iodines to it

proteolysis

when the precursor splits and creates T3, T4

thyroglobulin

thyroid hormone precursor

Na/I symporter

ions are transferred in the same direction

iodine move in with sodium

how T3 and T4 are made

1. iodine is brought into the cell by the capillaries dumping iodine to the Na/I symporter

2. the Na/I symporter brings in both iodine and sodium into the cell

3. the iodine gets shuttles across the cell to Pendrin

4. Pendrin then pumps iodine into the lumen of the follicle cell

5. once iodine is in the lumen, it is oxidized by thyroid peroxidase

6. at the same time, the follicular cell’s ER is budding off and it contains thyroglobin and gets exocytosed into the lumen at the same time as iodine

7. the thyrogloubin and oxidized iodine combine in the lumen

8. they undergo conjugation

9. they get endocytosed into the cell again

10. they then undergo proteolysis where the precursor gets split into T3 and T4

11. T3 and T4 are then dumped into the blood stream