Thyroid Gland Lopez Lecture

Question 1

Factors increasing T4 –> T3 conversion

Answer 1

obesity, cold, hyperthyroid

Question 2

factors decreasing T4 –> T3 conversion

Answer 2

pregnancy 
fasting
beta-blockers
hepatic/renal failure 
aging 
hypothyroid

Question 3

Enzymes converting T4 –> T3 into its active form

Answer 3

deiodinases type 1 and type 2

outer ring iodination

Question 4

Enzymes converting T4—> T3 into its inactive form

Answer 4

deiodinase type 3

inner ring iodination

Question 5

TSH Abs do what?

Answer 5

stimulate TH synthesis

Question 6

TH stimulatory factors

Answer 6

increased TBG levels such as during pregnancy

Question 7

What proteins are synthesized under the influence of thyroid hormones?

Answer 7

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

Question 8

Na-k ATPase

Answer 8

in most tissues it is stimulated by thyroid hormone

Question 9

proteins in cardiac muscle stimulated by TH

Answer 9

beta1 adrenergic receptors, Ca-ATPase

Question 10

what factors inhibit TH synthesis?

Answer 10

PTU 
thiocyanate 
percholate 
Wolff-Chakioff effect 
liver disease

Question 11

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

Answer 11

T4 has to be deiodinated by 5’ iodinase to T3

Question 12

What actions does TH have on the body?

Answer 12

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.

Question 13

What agens prevent the conversion of T4 to T3?

Answer 13

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

Question 14

Obesity

Answer 14

increases T4—> T3 conversion

Question 15

How does TH work inside the cell?

Answer 15

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

Question 16

TH effects on growth

Answer 16

bone maturation and growth formation

Question 17

TH on CNS

Answer 17

maturation of CNS

Question 18

TH on BMR

Answer 18

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

Question 19

TH on metabolism

Answer 19

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

Question 20

TH and cardiovascular

Answer 20

increases cardiac output

Question 21

What accounts for TH’s stimulation of metabolism?

Answer 21

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

Question 22

how does BMR increase under influence of TH?

Answer 22

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

Question 23

What effect does hypothyroidism have on BMR?

Answer 23

decreases it

Question 24

what effect does hyperthyroidism have on BMR?

Answer 24

increases it

Question 25

TH effect on lipid metabolism

Answer 25

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

Question 26

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

Answer 26

inverse

Question 27

what will blood cholesterol look like in patients with hypothyroidism?

Answer 27

it will be increased

Question 28

Vit. A and TH

Answer 28

TH is required for conversion of carotene to vitamin A hypothyroidism can suffer blindness/yellowing of skin

Question 29

carbohydrate metabolism

Answer 29

TH increases gluconeogenesis, glycogenolysis to generate glucose enhancement of insulin dependent entry of glucose into cells

Question 30

Cardiovascular effects DIRECT (7)

Answer 30

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

Question 31

Cardiovascular effects Indirect (4)

Answer 31

increased heat production decreased peripheral resistance decreased diastolic pressure increase in reflex adrenergic stimulation

Question 32

"ultimate" outcomes on the cardiovascular system due to TH

Answer 32

increase in cardiac rate and output increase in blood volume (direct and indirect)

Question 33

Type 1 deiodinase

Answer 33

found mostly in the peripheral tissues

Question 34

Type 2 deiodinase

Answer 34

found mostly in the brain

Question 35

Pendrin

Answer 35

the transporter for iodide across the apical surface of the follicular cell iodide, NOT iodine

Question 36

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

Answer 36

iodine (I2) and thyroglobulin with tyrosine moities

Question 37

intrathyroidal deiodinase = function?

Answer 37

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

Question 38

how much iodide will be taken up in the first 6 hours after injection? what % indicates hyperthyroidism? hypothyroidism?

Answer 38

25% 60% 10% roughly

Question 39

transthyretin

Answer 39

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

Question 40

what test can measure TBG?

Answer 40

T3 resin uptake test

Question 41

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

Answer 41

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

Question 42

T3 resin levels will increase during

Answer 42

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

Question 43

T3 resin uptake will decrease when

Answer 43

TBG is increased or endogenous T3 is decreased

Question 44

Thyroid hormones stimulate the

Answer 44

synthesis of cardiac beta-1 adrenergic receptors used by norepinephrine

Question 45

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

Answer 45

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

Question 46

bone formation is stimulated synergistically with

Answer 46

TH and GH and somatomedins

Question 47

deficient TH during perinatal years

Answer 47

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

Question 48

TH deficiency in children during the ____ period causes

Answer 48

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

Question 49

Metabolism: hypo/hyper

Answer 49

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

Question 50

Skin: hypo/hyper

Answer 50

hyper: excess sweating hypo: dry skin, myexidema

Question 51

Bone: hypo/hyper

Answer 51

hyper: osteoporosis hypo: stunted growth

Question 52

CV system: hypo/hyper

Answer 52

hyper: tachycardia, atrial fibrillation, palpitations, high-output heart failure hypo: bradycardia, decreased contractility, decreased cardiac output

Question 53

CNS: hypo/hyper

Answer 53

hyper: agitation, anxiety, difficulty concentrating, hyperreflexia hypo: cretinism (congenital) in kids, listlessness/slowed movement/somnolence/impaired memory/decreased mental capacity

Question 54

INTESTINE: hypo/hyper

Answer 54

hyper: diarrhea hypo: constipation