Thyroid Gland Lopez Lecture Flashcards Preview

COM Anatomy, Biochemistry, OS > Thyroid Gland Lopez Lecture > Flashcards

Flashcards in Thyroid Gland Lopez Lecture Deck (54):
1

Factors increasing T4 --> T3 conversion

obesity, cold, hyperthyroid

2

factors decreasing T4 --> T3 conversion

pregnancy
fasting
beta-blockers
hepatic/renal failure
aging
hypothyroid

3

Enzymes converting T4 --> T3 into its active form

deiodinases type 1 and type 2

outer ring iodination

4

Enzymes converting T4---> T3 into its inactive form

deiodinase type 3

inner ring iodination

5

TSH Abs do what?

stimulate TH synthesis

6

TH stimulatory factors

increased TBG levels such as during pregnancy

7

What proteins are synthesized under the influence of thyroid hormones?

Na-K ATPase
beta1 adrenergic receptor
lysosomal enzymes
proteolytic enzymes
structural proteins



8

Na-k ATPase

in most tissues it is stimulated by thyroid hormone

9

proteins in cardiac muscle stimulated by TH

beta1 adrenergic receptors, Ca-ATPase

10

what factors inhibit TH synthesis?

PTU
thiocyanate
percholate
Wolff-Chakioff effect
liver disease

11

what is the first step of TH in acting on target tissues?

T4 has to be deiodinated by 5' iodinase to T3

12

What actions does TH have on the body?

it acts on virtually all tissues of the body

creates heat, protein synthesis, increases basal metabolic rate, and oxygen consumption. acts synergistically with GH and somatomedins.

13

What agens prevent the conversion of T4 to T3?

hepatic failure, renal failure, beta adrengeric blocking agents, and pregnancy, fasting, stress

14

Obesity

increases T4---> T3 conversion

15

How does TH work inside the cell?

somehow it gets into the cell and binds to a nuclear receptor. it translocates to nucleus and stimulates nuclear transcription by binding to thyroid regulatory element on DNA

16

TH effects on growth

bone maturation and growth formation

17

TH on CNS

maturation of CNS

18

TH on BMR

increases synthesis of Na-K ATPases, O2 consumption, heat production, BMR

19

TH on metabolism

increase in glucose absorption, glycogenolysis, gluconeogenesis, lipolysis, protein synthesis and degradation (net catabolic)

20

TH and cardiovascular

increases cardiac output

21

What accounts for TH's stimulation of metabolism?

the synthesis of Na-K ATPases: leads to O2 consumption and heat production

22

how does BMR increase under influence of TH?

new Na-K ATPases: a single does of T4 (thyroxine) can increase BMR a few hours after injection, and long lasting (6 hrs)

23

What effect does hypothyroidism have on BMR?

decreases it

24

what effect does hyperthyroidism have on BMR?

increases it

25

TH effect on lipid metabolism

stimulates FA metabolism---> increases FA plasma levels, FA intake into the liver, beta oxidation of the FAs

26


TH have what kind of proportional relationship to cholesterol and glycerol?

inverse

27

what will blood cholesterol look like in patients with hypothyroidism?

it will be increased

28

Vit. A and TH

TH is required for conversion of carotene to vitamin A

hypothyroidism can suffer blindness/yellowing of skin

29

carbohydrate metabolism

TH increases gluconeogenesis, glycogenolysis to generate glucose

enhancement of insulin dependent entry of glucose into cells

30

Cardiovascular effects

DIRECT (7)

increases proteins in muscles

1) myosin heavy chain alpha/beta ratio

2) Na-K ATPase

3) G protein stim/inhibitory ratio

4) Sarcoplasmic Ca-ATPase

5) increases ventricular contractility and function

6) decreases peripheral vascular resistance

7) beta adrenergic signaling

31

Cardiovascular effects

Indirect (4)

increased heat production

decreased peripheral resistance

decreased diastolic pressure

increase in reflex adrenergic stimulation

32

"ultimate" outcomes on the cardiovascular system due to TH

increase in cardiac rate and output

increase in blood volume (direct and indirect)

33

Type 1 deiodinase

found mostly in the peripheral tissues

34

Type 2 deiodinase

found mostly in the brain

35

Pendrin

the transporter for iodide across the apical surface of the follicular cell

iodide, NOT iodine

36

what are the "two" main players in the lumen of the follicle?

iodine (I2) and thyroglobulin with tyrosine moities

37

intrathyroidal deiodinase = function?

breaks down the Thyroglobulin-MIT-DIT ---> TG, tyrosine, MIT, DIT

38

how much iodide will be taken up in the first 6 hours after injection?

what % indicates hyperthyroidism? hypothyroidism?

25%

60%

10% roughly

39

transthyretin

responsible for getting T4 to brain, kind of like thyroid binding globulin

40

what test can measure TBG?

T3 resin uptake test

41

the T3 resin test will indicate what general character of T3 during hepatic failure?

increased T3-bound resin, because there is a DECREASE in liver produced TBG

42

T3 resin levels will increase during

hepatic failure when TBG is decreased or when T3 levels are increased in the blood already

43

T3 resin uptake will decrease when

TBG is increased or endogenous

T3 is decreased

44

Thyroid hormones stimulate the

synthesis of cardiac beta-1 adrenergic receptors

used by norepinephrine

45

what branch of the nervous system is highly functioning when TH is high in the body, and why

sympathetic nervous system because beta adrenergic receptors are being produced in quantity. so when TH is high, there are more beta-adrenergic receptors on the heart for example

46

bone formation is stimulated synergistically with

TH and GH and somatomedins

47

deficient TH during perinatal years

leads to abnormal development of synapses
decreased dendritic branching and myelination
neutral changes induced by thyroid hormone deficiency cause cretinism

48

TH deficiency in children during the ____ period causes

perinatal = "of or relating to the time, usually a number of weeks, immediately before and after birth."

decreased dendritic branching and myelination
abnormal development of synapses

49

Metabolism: hypo/hyper

hyper: heat intolerance, weight loss, increased BMR
hypo: cold intolerance, weight gain, decreased BMR

50

Skin: hypo/hyper

hyper: excess sweating
hypo: dry skin, myexidema

51

Bone: hypo/hyper

hyper: osteoporosis
hypo: stunted growth

52

CV system: hypo/hyper

hyper: tachycardia, atrial fibrillation, palpitations, high-output heart failure

hypo: bradycardia, decreased contractility, decreased cardiac output

53

CNS: hypo/hyper

hyper: agitation, anxiety, difficulty concentrating, hyperreflexia

hypo: cretinism (congenital) in kids, listlessness/slowed movement/somnolence/impaired memory/decreased mental capacity

54

INTESTINE: hypo/hyper

hyper: diarrhea
hypo: constipation