Part 16: Thyroid Disorders

Question 1

thyroid hormones are involved in what physiologic processes (6)?

Answer 1

1. metabolism
2. energy expenditure
3. body temp
4. promote growth and differentiation of cells
5. bone remodelling
6. protein synthesis and degradation

Question 2

higher levels of thyroid hormones tends to cause ____ (increased or decreased) metabolism

Answer 2

increased

Question 3

t/f thyroid hormones can be increased to a pathologic level which can cause overactive cellular processes

Answer 3

t

Question 4

by increasing energy expenditure & metabolism, thyroid hormones increase ____ utilization and _____ oxidation

Answer 4

glucose; fatty acid

Question 5

thyroid hormones have ___ (sympatholytic or parasympatholytic) effects

Answer 5

sympath

Question 6

what is the effect of thyroid hormones on heart rate

Answer 6

raise hr

Question 7

thyroid hormone secretion is regulated by the ___ and ___ glands

Answer 7

hypothalamus & pituitary

Question 8

thyroid hormones are typically secreted in parallel with ____ rhythms

Answer 8

circadian

Question 9

at what time of day is the highest amount of thyrotropin released from the hypothalamus?

Answer 9

2-4 am, when most people are sleeping

Question 10

TRH stimulates the pitutary gland to secrete ____

Answer 10

TSH

Question 11

the release of TSH from the pituitary causes the release of 2 thyroid hormones ___ & ___

Answer 11

T3 & T4

Question 12

TRH stands for

Answer 12

thyrotropin releasing hormone

Question 13

what are 2 positive regulators of TRH?

Answer 13

psychosis & cold temperature

Question 14

what is a negative regulator of TRH?

Answer 14

stress

Question 15

what is a negative regulator of TSH?

Answer 15

cortisol (stress)

Question 16

what is the only structural difference between T3 & T4?

Answer 16

one iodine group

Question 17

which thyroid hormone has higher affinity for the thyroid hormone receptors?

Answer 17

T3

Question 18

the majority of thyroid-related physiologic effects are the result of thyroid hormone receptors being activated by which hormone?

Answer 18

T 3

Question 19

what enzyme in the follicular cells of the thyroid is responsible for thyroid hormone synthesis and storage of the hormones as thyroglobulin comblexes?

Answer 19

thyroid peroxidase

Question 20

once the thyroid hormones are made, they are stored as ___

Answer 20

thyroglobulin complexes

Question 21

thyroid hormones are made from dietary ___

Answer 21

iodine

Question 22

t/f the thyroid gland is the only human organ that uses iodine

Answer 22

t

Question 23

does the thyroid gland create small amounts of hormone PRN or does it makes lots and store it?

Answer 23

makes lots and stores it

Question 24

when stimulated by TSH, the ____ is cleaved and thyroid hormones are released into circulation

Answer 24

thyroglobulin

Question 25

which of the 2 thyroid hormones is secreted in greater amount?

Answer 25

t4

Question 26

how does thyroid peroxidase make thyroid hormones?

Answer 26

adds iodine groups to tyrosine residues and groups 2 iodinated tyrosine together

Question 27

thyroid hormones circulate in the blood, primarily bound to ____ protein

Answer 27

thyroid-binding globulin

Question 28

T4 is taken up by target cells via _____ transporters

Answer 28

organis anionic (OAT)

Question 29

when T4 is taken up by OATS into target cells, it is converted into ___ by

Answer 29

T3

Question 30

what enzymes are responsible for turning T4 into T3

Answer 30

cellular deiodinases

Question 31

T3 binds to thyroid hormone receptors in the ____ of target cells

Answer 31

nucleus

Question 32

activation of nuclear thyroid hormone receptors alters gene ___, which results in increasded cellular ___ and ____

Answer 32

transcription; metabolism & activity

Question 33

nuclear receptors are classed with intracellular receptors and are sometimes called _____

Answer 33

ligand-activated transcription factprs

Question 34

T4 has a ____ (long or short) half-life

Answer 34

long

Question 35

what is the rate limiting step in the process of thyroid causing physiologic effects?

Answer 35

the converesion of T4 to T3

Question 36

T4 is almost like an endogenous _____drug

Answer 36

pro

Question 37

what is the half-life of T4?

Answer 37

6-7 days

Question 38

hyperthyroidism presents as symptoms associated with ___ metabolic rate

Answer 38

increased

Question 39

hypothyroidism presents as symptoms associated with ___ metabolic rate

Answer 39

decreased

Question 40

the circulating thyroid hormones impose ____ feedback loops on the release of TSH and TRH

Answer 40

negative

Question 41

the 2 most common thyroid disorders are autoimmune diseases and are :

Answer 41

1. graves (hyper) | 2. hashimoto's (hypo)

Question 42

graves disease is the most common clinical presentation of _____

Answer 42

hyperthyroidism

Question 43

in Grave's disease, a stimulatory anti-body called _____ is made by the immune system and it will stimulate ____ receptors to promote thyroid hormone release

Answer 43

thyroid-stimulation immunoglobulin; TSH

Question 44

why can the thyroid-stimulating IG continue to cause the release of thyroid hormones even when a negative feedback loop is present?

Answer 44

it is not sensitive to the negative feedback loop

Question 45

Case: a patient presents with high levels of T4, but low levels of TSH, what is the likely diagnosis?

Answer 45

likely graves disease hyperthyroidism bc the IG would bind to the TSH receptor to promote more T4 even though there is a negative feedback loop to reduct the amount of TSH made

Question 46

in Grave's disease ____ hormone is high and ___ and ___ hormones are low

Answer 46

T4; TRH and TSH

Question 47

what are some clinical symptosm of Grave's disease/ hyperthyroidism?

Answer 47

fast heart rate, weight loss (despite eating more) , elevated body temp. Extreme cases can have bulging eyes, goiter, and tremour

Question 48

what causes a goiter?

Answer 48

increased production of thyroid hormone

Question 49

what causes bulging eyes in Grave's disease?

Answer 49

inflammation & edema

Question 50

what are some long-term consequences of untreated hyperthyroidism?

Answer 50

osetoporosis, peridontal disease, increased risk for "thyroid storm" and thyrotoxic risk

Question 51

what is thyroid storm?

Answer 51

a life-threatening situation where there is a sudden onset of systemic symptoms such as sweating, raised body temp, increased HR , dyspnea, muscle weakness, and cognitive changes

Question 52

thyroid storm can be triggered by ____ during a prolonged period of uncontrolled hyperthyroidism

Answer 52

systemic triggers like an infection

Question 53

what is methimazole?

Answer 53

a thyroid hormone antagonist

Question 54

t/f there is typically a delay in onset of thyroid antagonsists and they are not always 100% successful in managing hyperthyroidism, but do reduce the production of thyroid hormones

Answer 54

t

Question 55

methimazole is an antagonist of _____ (enzyme)

Answer 55

thyroid peroxidase

Question 56

is methimazole a competitive or non-competitive inhibitor?

Answer 56

competitive

Question 57

methimazole reduces the ____ synthesis of thyroid hormones

Answer 57

de novo

Question 58

why do the effects of methimazole take several weeks to kick in?

Answer 58

bc the thyroid gland has a lot of thyroid hormones already stored and ready to go, so you need to wait until that supply has been depleted

Question 59

methimazole is part of the ___. class

Answer 59

thioamide

Question 60

thioamides like methimazole have what important consideration in pregnancy?

Answer 60

they may interfere with fetal thyroid hormone synthesis and can cause hypothyroidism in the fetus

Question 61

what is the typical approach to methimazole use in pregancy?

Answer 61

it is also risky to have too high thyroid hormone, so methimazole may be used in pregnancy, but doses and serum level of thyroid hormones will be closely monitored

Question 62

t/f thioamides cross the placemta

Answer 62

t

Question 63

what are some of the pregancy risks associated with hyperthyroidims?

Answer 63

spontaneous abortion, low birth weight, stillbirth, preeclampsia, and heart failure

Question 64

list 2 examples of more complete methods of reducing thyroid hormones?

Answer 64

destruction of the thyroid gland with radioactive iodine or surgical removal

Question 65

why is systemic radioactive iodine not Thatttt unsafe?

Answer 65

bc the thyroid gland is the only organ that takes it up and uses it, so only the thyroid will be destroyed

Question 66

is the treatment with radioactive iodine immediate for reducing thyroid hormone?

Answer 66

no, because there is still the stored hormone

Question 67

t/f radioactive iodine treatment results in a dose-dependent irreversible termination of thyroid hormone productio

Answer 67

t

Question 68

t/f most patients treated with radioactive iodine will need surgical removal later bc it is difficult to know the exact dose needed of the iodine to completely inhibit the thyroid

Answer 68

t

Question 69

t/f the removal of the thyroid gland puts patients in a hypothyroid state and will require supplementation

Answer 69

t

Question 70

what is hypothyroidism?

Answer 70

thyroid hormone levels are too low to properly maintain metabolic and cellular functions

Question 71

what is Hashimoto's thyroditis?

Answer 71

a form of hypothyroidim caused by an autoimmune disorder in which the autoantibody destroys the thyroid gland

Question 72

t/f Hashimoto's results in low thyroid hormone levels despite the hypothalamus and pituitary calling for more release

Answer 72

t

Question 73

Case: patient is persistently cold and tired, gaining weight despite eating well, her T4 is low and TSH is high

Answer 73

she has hyperthyroidism

Question 74

which sex has higher rates of hypothyroidism?

Answer 74

female

Question 75

is hypothyroidism more common in younger or older people/

Answer 75

older

Question 76

hypothyroidism during development will have what effect on growth?

Answer 76

slowed growth

Question 77

the heart rate and BP of hypothyroid patients will be ____ (higher/lower) than normal

Answer 77

lower

Question 78

edema and enlarged tongue are symptoms of what type of thyroid disorder?

Answer 78

hypo

Question 79

what is a common drug used to treat hypothyroidism?

Answer 79

levothyroxine (synthroid)

Question 80

what is levothyroxine?

Answer 80

a synthetic T4 hormone

Question 81

t/f the doses of synthroid need to be titrated over time

Answer 81

t

Question 82

is the GI absorption os synthroid affected by food?

Answer 82

yes

Question 83

which has a longer half-life, synthroid, T4, or liothyroxine

Answer 83

synthroid

Question 84

the TH effects of synthroid are controlled by the physiological conversion to ____-

Answer 84

T3

Question 85

what is Liothyroxine and why is it not preferred?

Answer 85

a synthetic T3 hormone, not preferred bc it has higher risk for hyperthyroidism

Question 86

why is the risk for hyperthyroidism higher in liothyronine than synthroid?

Answer 86

bc liothyronine skips the rate limiting step of converting T4 to T3

Question 87

do patients continue thyroid medications for life?

Answer 87

yes

Question 88

can lifestyle changes affect the dose of thyroid drugs needed?

Answer 88

yes

Question 89

the biovailabilty of synthroid is increased on a full or empty stomach?

Answer 89

empty

Question 90

the demand for thyroid hormones is ofetn ___ (higher or lower) during pregnancy

Answer 90

higher

Question 91

people on any type of thyroid medication need routine ____

Answer 91

blood wrk