Thyroid Gland

Question 1

Describe the location of the thyroid gland

Answer 1

Below the Larynx

Question 2

What connects the thyroid glands anteriorly?

Answer 2

Isthmus - thyroid tissue

Question 3

What are the hormones secreted by the thyroid gland?

Answer 3

• Thyroxine (T4)
• Triiodothyronine (T3)

Question 4

_______________ are the follicular cells that line the thyroid follicles and are cuboidal shaped.

Answer 4

Thyrocytes

Question 5

Parafollicle cells (C cells) secrete the hormone _________________

Answer 5

Calcitonin (thyrocalcitonin)

Question 6

Which Thyroid hormone is the most active but with a short half life?

Answer 6

T3 - triiodothyronine

Question 7

What do T4 and T3 bind to for travel in blood?

Answer 7

Bound to plasma proteins

Question 8

What is the plasma protein that T4 and 3 bind to ?

Answer 8

Thyroxine-binding globulin (TBG)

Question 9

What converts T4 to T3 once they enter target cells?

Answer 9

Deiodinase

Question 10

T3 and T4 are made by ______________ after iodinization

Answer 10

Tyrosines

Question 11

What is the precursor for tyrosine ?

Answer 11

Thyroglobulin (TG)

Question 12

TG is the major protein component of what part of the follicular cells ?

Answer 12

Follicle colloid

Question 13

What accumulates in thyroid follicles from the blood to then be secreted onto the colloid?

Answer 13

Iodide (I-)

Question 14

Once Iodide enters the colloid through what process is it converted into iodine (I2)?

Answer 14

Oxidation

Question 15

_____________ are attached to the AA ____________ within the T.

Answer 15

Iodines / tyrosine

Question 16

One iodine + Tyrosine = molecule ?

Answer 16

Monoidotyrosine (MIT)

Question 17

DIT (diiodotyrosine) is the attachment of how many iodines?

Answer 17

2

Question 18

How many DIT molecules are needed to produce tetraiodothyronine or T4?

Answer 18

2

Question 19

MIT + DIT = ?

Answer 19

Triiodothyronine T3

Question 20

Where in the follicular cell does the TH synthesis occur?

Answer 20

Thyroid follicles

Question 21

What is the process through which the thyroid follicles take up colloid volume when stimulated by TSH?

Answer 21

Pinocytosis

Question 22

Which TH is lipophilic, meaning it can diffuse accross the plasma membrane?

Answer 22

T4

Question 23

Which enzyme converts T4 into T3 in the cytoplasm?

Answer 23

Deiodinase

Question 24

The hormone receptor complex that forms is due to the binding of T3 or T4 to non specific proteins?

Answer 24

T3 binds and enters the nucleus with NSP

Question 25

Which receptors are needed to for the TH to activate gene expression?

Answer 25

TR (thyroid hormone Receptor) and RXR (retinoid X receptor)

Question 26

The vitamin A derivative 9-cis-retinoic acid is associated with which receptor?

Answer 26

RXR

Question 27

TH on metabolism can induce ________________, and thus ATP production

Answer 27

cell respiration

Question 28

T/F TH can increase the basal metabolic rate

Answer 28

True

Question 29

If food intake with an increased BMR does not increase, list some things that may happen

Answer 29

- lipolysis - protein breakdown - N2 excretion

Question 30

TH on skeletal muscle can stimulate synthesis of what ?

Answer 30

Proteins (myosin heavy)

Question 31

To Which muscle type fiber switch is stimulated by TH?

Answer 31

Fast-twitch fibers (white/type II)

Question 32

With hypothyroidism, one can expect ____________________ to occur in relation to skeletal muscle

Answer 32

muscle weakness

Question 33

With hyperthyroidism, one can expect the overcontraction of muscles and thus degeneration, which is termed:

Answer 33

Thyrotoxic myopathy

Question 34

Do TH increase or decrease O2 consumption and CO?

Answer 34

Increase it, thus increase HR

Question 35

The lack of TH during development can lead to __________________

Answer 35

Cretinism

Question 36

TH can ___________ (increase or decrease) the sensitivity to catecholamines

Answer 36

Increase by increasing expression of the receptors

Question 37

Thyrotropin (TSH) and TRH (thyrotropin releasing hormone) will do what to Th secretion?

Answer 37

It will augment it

Question 38

Activation of T3 and T4 synthesis/secretion pathways is done by which hormone associated with TH?

Answer 38

TSH (thyrotropin)

Question 39

An enlarged thyroid gland is termed:

Answer 39

Goiter

Question 40

Goiter can be:

Answer 40

Endemic or toxic

Question 41

Endemic goiter is due to a deficiency in what?

Answer 41

Iodine

Question 42

In endemic goiter, are TSH secretion levels abnormally high or abnormally low?

Answer 42

Abnormally high

Question 43

T/F TH levels are normal or a little low in a patient with endemic goiter

Answer 43

True - the abnormal growth of thyroid follicles compensate the inadequate TH production

Question 44

What is another name for toxic goiter?

Answer 44

Thyrotoxicosis (Grave's disease)

Question 45

What is the cause for Grave's disease/Thyrotoxicosis?

Answer 45

Autoantibody (TSI: thyroid stimulating immunoglobulin) binding to TSH receptor

Question 46

T/F Toxic goiter can be found in animals

Answer 46

False

Question 47

Which can be seen with thyrotoxicosis - hyper or hypo thyroidism?

Answer 47

Hyperthyroidism

Question 48

What is the most common cause of feline hyperthyroidism?

Answer 48

Benign thyroid tumor

Question 49

List clinical signs associated with feline hyperthyroidism

Answer 49

- weight loss - hyperactivity - palpable goiter - unkempt coat

Question 50

Lymphocytic Thyroiditis or Idiopathic thyroid gland atrophy are common cause of canine __________________

Answer 50

hypothyroidism

Question 51

Obesity, Skin DZ, Lethargy and cold intolerance are signs associated with?

Answer 51

Hypothyroidism in dogs