Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

END 207: Physiology > Endocrine 5: Thyroid Hormone > Flashcards

Endocrine 5: Thyroid Hormone Flashcards

1
Q

enumerate Hormones secreted by thyroid gland

A

Thyroid hormones:
* Thyroxin (T4)
* Tri-iodothyronine (T3)

Thyrocalcitonin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Describe formation of thyroid hormones

A

1.Thyroglobulin (colloid) synthesis:
* gycoprotein rich in tyrosine aa
* It’s then secreted into Cavity of thyroid follicle along with peroxidase enzyme

2.Iodide trapping:
* Na+ K+ATPase pumps Na+ out of cell, decreasing its concentration inside the cell
* Na+ is then Cotransported with I- (iodide) inside the cell
* Iodide is co-transported against electrochemical gradient by 8:1

3.Oxidation & Iodination:
* Peroxidase oxidised Iodide into iodine
* Peroxidase binds iodine to thryoglobulin
* this forms MIT & DIT (mon-iodo & di-iodo tyrosines)

  1. Coupling:
    * 2 DIT form T4
    * 1 DIT & 1 MIT form T3
    * 1 MIT & 1 DIT form rT3
  2. Release:
    * transported into cell by pinocytosis
    * pinocytic vesicle merges with lysosome, where proteinase liberates T4, T3, & remaining DIT & MIT of thyroglobulin
    * T4 & T3 diffuse to nearby capillaries
    * DIT & DMT have their Iodine removed by Iodotyrosine deiodinase enzyme
    * the Iodine is then recycles to make more T3 & T4

6.Storage of excess hormones in center of follicle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Other sites of iodide trapping in the body

A
  • Mammary gland
  • salivary gland
  • gastric mucosa
  • placenta
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

ratio of T4:T3:rT3

A

40:2:1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Daily Iodine requirements

A

500 micrograms:
* 4/5 are rapidly excreted by th kidney
* 1/5 (100 micrograms) undergo iodine trapping

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Describe how the body can cover any deficiency in daily iodine intake

A

Storage of Thyroid hormones central follicular cavity

covers up to 2-3 months of deficient intake

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Thyroid gland secretes ____ micrograms of thyroid hormones per day

A

70 micrograms per day

93% T4, 7% T3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Percentage of T4 that is bound

A

99.98%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Percentage of T3 that is bound

A

99.8 %

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Thyroid hormones are carried in the blood via:

A
  • Albumin
  • Thyroxine binding prealbumin (TBPA)
  • Thyroxine binding globulin
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

which carrier has the highest affinity to thyroid horomones

A

globulin:
* 2/3 of T4
* 1/2 of T3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

least active/ inactive thyroid hormone

A

rT3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Most active thyroid hormone, and why

A

T3:
* More free (less bound to plasma proteins)
* 10-15 more affine to thyroid receptors than T4

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

T3 binds to what type of thyroid receptors

A

T3= 3 receptors
all beta + alpha 1
* Beta 1
* Beta 2
* Alpha 1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

sites of thyroid receptors

A
  • Extranuclear for non-genomic actions (cell membrane, cytoskeleton, cytoplasm mitochondria)
  • Nuclear (bound to DNA) for genomic actions
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

effect of thyroid hormone on genral cellular metabolism

A

Calorigenesis & Increases O2 Consumption:
* Increase in number & Size of mitochondria - In excess, may lead to mitochondrial swelling & uncoupling of oxidative phosphorylation with little increase in ATP and greater loss of heat
* Increases the activity of Sodium potassium pump

17
Q

effect of thyroid hormone on Carbohydrate metabolism

A
  • increase insulin secretion
  • Increase glucose uptake by the cell
  • increase glucose absorption by GIT
  • Increase glycolysis
  • Increase gluconeogenesis
18
Q

effect of thyroid hormone on Lipid metabolism

A

overall decrease in blood lipids:
* Lipolysis & mobilization of lipids from fat tissue
* Increase FFA oxidation
* Decrease plasma cholesterol by:
1.increase cholesterol secretion in bile
2.increase LDL receptors of liver –> rapid removal of LDLs from plasma
3.Increase cholesterol oxidation by the cells

19
Q

effect of thyroid hormone on Protein metabolism

A

(anabolic) increases protein synthesis

20
Q

effect of thyroid hormone on Vitamin metabolism

A

general increase in enzyme activity —> increase in body reqirements for coenzymes (vitamins)

21
Q

effect of thyroid hormone on BMR, BEE & body weight

A

normal levels of TH are responsible for normal BMR & BEE (40 calories/hr/m2) & normal body weight = energy balance

22
Q

effect of thyroid hormone on growth

A
  • Mental growth and development
  • Neuronal, axonal & nerve ending formations
  • Skeletal growth
  • Sexual growth (along with hormones)
23
Q

effect of thyroid hormone on body systems

A
  • primary effect: direct hormonal action
  • secondary effect: increase metabolism of various systems –> caloregic action (increase O2 consumption)
24
Q

where in the body does o2 consumption decrease by thyroid hormone

A

Anterior pituitary gland (negative feedback)

25
Q

where in the body does o2 consumption doesn’t increase by thyroid hormone

A
  • Testis & uterus
  • ADULT brain
  • Spleen
  • Lymph nodes
26
Q

Describe the hypothalamic -pituitary regulation of Thyroid hormone

A
  1. Hypothalamus secretes TRH (thyrotropin releasing hormone) through hypothalamo-hypophyseal portal circulation
  2. TRH binds to thyrotrope receptors in Anterior pituitary –> G protein –> phosphlipase –> increase intracellular Ca2+ –> release of Thyrotropin/ Thyroid stimulating hormone into systemic circulation
  3. TSH binds to receptors on basal mmebrane of thyroid gland cells —> G protein –> Adenyl cyclase –> cAMP –> protein kinase –> phosphorylations

Witihin 30 mins of phosphorylation: increased thyroglobulin proteolysis

Within hours, days weeks: Activation of iodide pump making 8:1 iodide (intracellular to extracellular) + increase tyrosine iodinasation + increase in number & size of thyroid gland cells

27
Q

describe feedback regulation of thyroid hormones

A

done by T3:
* both T3 & T4 directly decrease TSH/thyrotropin production in pituitary gland
* T4 is converted first to T3 to exert feedback effect

END 207: Physiology (20 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions