Lecture 68

Question 1

_______ controls thyroid hormone secretion?

Answer 1

Negative feedback

Question 2

Negative feedback exerted predominantly at _______ to decrease TSH

Answer 2

anterior pituitary

Question 3

_______ provides feedback

Answer 3

T3

Question 4

TSh is tonically inhibited by _______ and _______ from hypothalamus

Answer 4

Dopamine and somatostatin

Question 5

TSH can also be inhibited by?

Answer 5

cortisol and GH

Question 6

Thyroid hormones decrease the sensitivity of the anterior pituitary to TRH thereby decreasing _______?

Answer 6

TSH secretion

Question 7

Hypothalamic nuclei secrete TRH into

Answer 7

portal vessels

Question 8

Negative feedback: Slightly pulsible TSH and fairly

Answer 8

steady T3 and T4

Question 9

during fasting TSH response to TRH will

Answer 9

diminish and T3 falls (decrease metabolic rate)

Question 10

TRH stimulates

Answer 10

TSH

Question 11

Meal or cold exposure increases _______

Answer 11

T3 availability

Question 12

T4 deiodinated equally to active T3 and rT3 within

Answer 12

tissues

Question 13

if more thyroid hormone action needed, get more T3 relative to

Answer 13

rT3 and vise versa

Question 14

_______ converts T4 to T3

Answer 14

5’ deiodinase

Question 15

_______ converts T4 to rT3

Answer 15

5 deiodinase

Question 16

starvation effects on conversion: inhibition of 5’ deiodinase

Answer 16

lower metabolism rate and O2 consumption

Question 17

during starvation effects does the brain 5’ deiodinase get effected?

Answer 17

NO

Question 18

during starvation effects the brain 5’ deiodinase does not get effected: more T3 if _______, less T3 if critically ill

Answer 18

cold

Question 19

_______ are major sites of degradation of thyroid hormones

Answer 19

Liver, kidneys, skeletal muscle

Question 20

some T4 excreted in

Answer 20

bile

Question 21

How does T4 enter cells?

Answer 21

Facilitated diffusion

Question 22

T4 is deiodinated to T3 where?

Answer 22

Inside cells

Question 23

How is T4 deiodinated to T3 inside cells?

Answer 23

5’ deiodinase

Question 24

T3 binds receptors within

Answer 24

nucleus of cell

Question 25

T3- receptor complex binds to _______ on DNA to stimulate transcription of genes

Answer 25

Thyroid-regulatory element

Question 26

Translation and new synthesis of proteins tend to be tissue

Answer 26

specific depending on effect

Question 27

how can thyroid hormones enter cells?

Answer 27

* Na/ K ATPase * Transport proteins * B1 adrenergic receptors * proteolytic enzymes

Question 28

Increased oxygen consumption and increased Na/ K ATPase is associated with

Answer 28

increased cell activity

Question 29

thyroid hormones increase cardiac output and pulse pressure (increased synthesis of

Answer 29

B-1 adrenergic receptors (Increase HR)

Question 30

effect of thyroid hormones on BMP: Increase

Answer 30

thermogenesis

Question 31

thyroid hormones increase supply of substrates for production of energy. Need substrates for oxidation. Increase _______?

Answer 31

* Mobilize glucose * Gluconeogenesis * absorption of glucose from GIT * lipolysis * FFA oxidation

Question 32

how does thyroid hormones affect appetite, gut absorption and motility

Answer 32

Increases

Question 33

Thyroid hormones also increases mobilization of

Answer 33

carbs and fat

Question 34

Protein synthesis vs degradation dependent on thyroid hormone levels: If thyroid hormone levels are normal

Answer 34

protein synthesis predominates

Question 35

Protein synthesis vs degradation dependent on thyroid hormone levels: If thyroid hormone levels are high

Answer 35

protein degradation predominates AA for energy

Question 36

_______ is required for normal growth

Answer 36

Thyroid hormones

Question 37

Thyroid hormones act with GH and IGFs to promote?

Answer 37

Growth of bone, cartilage, teeth, epidermis and hair

Question 38

Thyroid hormones are essential for normal maturation of

Answer 38

CNS

Question 39

Thyroid hormones increase blood flow and glucose metabolism in the

Answer 39

brain

Question 40

Thyroid hormones enhance

Answer 40

peripheral nerve reflexes (activates skeletal muscles and deep tendon reflexes)

Question 41

Thyroid hormones interact with SNS to have similar effects on increasing

Answer 41

cardiac output and heat production etc.

Question 42

Thyroid hormones in the ANS activate

Answer 42

Smooth and cardiac muscle

Question 43

_______ is it when there is an overactive thyroid, excess thyroxine

Answer 43

Hyperthyroidism

Question 44

_______ are the clinical signs of hyperthyroidism

Answer 44

Increased metabolic rate, food intake, heat production, heart rate, weight loss, muscle weakness and atrophy

Question 45

Hyperthyroidism is common in?

Answer 45

Cats

Question 46

Hyperthyroidism is common in cats due to adenoma, adenocarcinoma and thyroid disruptors including

Answer 46

Flame retardants (thyroid disruptors)

Question 47

Hyperthyroidism is seen in horses and dogs usually do to?

Answer 47

Thyroid adenocarcinoma

Question 48

_______ is high in hyperthyroidism?

Answer 48

T3 and t4

Question 49

If hyper disorder is in thyroid gland, TSH is

Answer 49

LOW

Question 50

Over producing thyroid hormones lots of T3 for negative feedback so

Answer 50

TSH is inhibited

Question 51

If hyperthyroidism disorder is in hypothalamus or pituitary, TSH is

Answer 51

HIGH

Question 52

When hyper disorder in in hypothalamus or pituitary, TSH is high, over producing TSH constantly

Answer 52

stimulates thyroid hormones

Question 53

Typical blood for hyper tests show low _______ and high _______

Answer 53

TSH, T4

Question 54

underactive thyroid, low thyroid hormones

Answer 54

Hypothyroidism

Question 55

decrease metabolic rate, cardiac output, cold intolerance, decrease sweating, weight gain are signs of

Answer 55

Hypothyroidism

Question 56

Lacking enzymes to make thyroid hormones

Answer 56

Congenital cretinism - thyroid dwarf

Question 57

Acquired hypothyroidism is common id dogs, rare in cats or horses

Answer 57

Usually immune mediated or idiopathic ( destruction of gland or blocking hormone synthesis)

Question 58

T3 and T4 is _______ in hypothyroidism

Answer 58

low

Question 59

If issue is in hypothalamus or pituitary gland for central hypothyroidism (TSH is Low) Not producing TSH as normal so no stimulus for

Answer 59

T4/T3

Question 60

If issue is in thyroid gland, TSH is high (most common; overt primary hypothyroidism)

Answer 60

not producing thyroid hormones so pituitary constantly stimulating to produce TSH

Question 61

typical blood test for hypothyroidism shows

Answer 61

high TSH and low t4

Question 62

Only "healthy" animals should be tested for thyroid function, as overt illness can

Answer 62

alter circulating thyroid hormone concentration