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Flashcards in Welch- thyroid Deck (80):
1

Regulation of thyroid hormone secretion

TRH --> TSH --> T3/T4

2

4 things that inhibit TSH

1) SS (SST)
2) dopamine
3) high levels of glucocorticoids
4) retinoids

3

what is needed for thyroxine synthesis but at high levels can also inhibit synthesis and release

I-

4

1) increases synthesis and release of TSH
2) effects on pituitary are mediated via cAMP
3) TRH releases prolactin (may be PRH)

TRH
-tripeptide

5

synthetic TRH

PROTIRELIN (Thypinone)

6

use of Protirelin

-DIAGNOSTIC to figure out where the problem is
-administer TSH and measure TSH and thyroid hormones

7

Where is the problem: Admin protirelin --> no change in TSH or T3/T4

Pituitary defect

8

Where is the problem: admin protirelin --> increase TSH --> no change in T3/T4

thyroid defect

9

Where is the problem: admin protirelin --> increase in TSH --> increase in T3/T4

Hypothalamus defect

10

Thyrotropin

TSH; glycoprotein

11

1) increases all aspects of synthesis
2) maintains integrity of the thyroid

TSH

12

-DEFICIENCY LEADS TO ATROPHY

TSH

13

-excess leads to increase vascularity, hypertrophy and hyperplasia

TSH

14

Clinical drug for TSH

THYTROPAR

15

what two thyroid hormones are only used diagnostically to figure out where the problem is

TRH and TSH

16

what condition is thytropar given to diagnose?

HYPOthyroidism

17

two enzymes that convert T4 --> T3

Deiodinase 1 and 2

18

what enzyme works in the LIVER, kidney and thyroid?

Deiodinase 1 (Exam)

19

what enzyme works in the brain, pituitary, heart, brown adipose tissue, skeletal muscle and thyroid

Deiodinase 2 (Exam)

20

What enzyme works in placenta, skin, brain, uterus, sites of inflammation to convert T4 --> rT3?

Deiodinase 3

21

True/False: T3 is more potent and more protein bound than T4

TRUE

22

Do you give T3 or T4 in an emergency situation?

T3 bc it has a fast onset (3 hr) and half life of 2 days

23

What do you give to stabilize someone?

T4 bc slow onset (24 hrs) and long half life (6-7 days)

24

what thyroid receptor isoforms are the main ones bound by T3 and T4

T3 and T4 both bind alpha and beta isoforms, but T3 has a higher affinity (10x greater affinity for the receptor)

25

deiodination of T4 --> T3 occurs where?

20% in LIVER

26

metabolic effect of thyroid hormones

increase utilization of CHO

27

1) increase BMR, spec in heart, diaphragm, liver and kidney; impt for temp regulation
2) increase # of adrenergic beta receptors in heart and sensitize heart to catecholamines (Exam)

calorigenic effect of thyroid hormones

28

-stimulate protein synthesis in most organs
-control cell proliferation in brain

regulation of growth and development by thyroid hormones

29

early cause of hypothyroidism back in the day

lack of iodine in foods

30

4 types of hypothyroidism

1) adult myxedema
2) Gull's disease (severe form- rare)
3) adult hypothyroidism/goiter
4) Hashimoto thyroiditis
5) juvenille myxedema/creitinism

31

-lack of embryonic development
-drug induced- iodides, Li etc
-neoplasia

etiology for primary adult hypothyroidism

32

defective TSH secretion

etiology for secondary adult hypothyroidism

33

defective TRH secretion

etiology for tertiary adult hypothyroidism

34

main symptom for primary adult myxedema

GOITER

35

main symptom for secondary and tertiary adult myxedema

ATROPHY

36

edema, thick rough skin, loss of hair, intolerance to cold, lethargy, dullness, anorexia, constipation, anemia, amenorrhea, infertility

symptoms for adult myxedema

37

primary hypothyroidism --> decreased T4 --> increased TRH --> increased prolactin --> interferes w/LH/FSH

hypothyroid induced infertility/amenorrhea

38

mild form, effects 6-7 mill americans, mostly women > 40

adult hypothyroidism

39

overdose of antithyroid or 131I or I2 deficiency

mild form of adult hypothyroidism

40

simple goiter, fatigue, muscle cramps, intolerance to cold etc

symptoms of adult hypothyroidism

41

immunologic disorder

Hashimoto thyroiditis

42

humoral immunity in the presence of antithyroid antibodies- inflammation

Hashimoto thyroiditis

43

I2 deficiency in kids

endemic cretinism

44

lack of thyroid development in kids

sporatic cretinism

45

drawrfism, short extremities, mental retardation, hypo activity, hypothermia, slow heart rate etc

cretinism

46

role of thyroid hormones in the brain

required for myelination of neurons

47

T4 DOC for hypothyroidism used in most cases

Levothyroxine (synthroid, levothyroid)

48

T3 drug for hypothyroidism

Liothyronine (cytomel)

49

drug used in emergency situation for quick onset like in coma in hypothyroidism

Liothyronine

50

Drug in a 4:1 ratio of T4:T3 used for hypothyroidism

Liotrix (Euthroid, thyrolar)
-little advantage and more $$$

51

thyroglobulin (Proloid)

drug used to tx hypothyroidism for ppl that lack thyroglobulin

52

Thyroid desiccated (armour thyroid, thyro-teric)

drug used to tx hypothyroidism

53

what drug displaces T3 and T4 from its binding sites

ASPIRIN

54

what is the most important thing with thyroid drugs

BINDING

55

If a drug increases binding of T3/T4 to TBG, what do you have to do to the dose?

Increase the dose, since bound drug doesn't have any effect

56

If a drug decreases binding of T3/T4 to TBG, what do you have to do to the dose?

Decrease the dose

57

Basedow's disease

another name for Grave's Disease (hyperthyroidism)

58

effects females 20-40 yrs, AI response; Abs stimulate TSH receptors on thyroid; no negative feedback

Grave's

59

thyrotoxicosis (can lead to right heart failure and a-fib), opthalmopathy, diffuse toxic goiter, young adults, spontaneous remission in 50% of cases

Grave's

60

toxic nodular goiter

Plummer's disease

61

-arises from long standing non-toxic goiter

Plummer's

62

opthalmopathy is uncommon, no spontaneous remission, older pts

Plummers

63

what are both Grave's and Plummer's missing

negative feedback

64

tachycardia, excitability, tremors, wt loss, heat intolerance, exopthalmos (less common in Plummer's), diarrhea, CHF (infrequent), arrhthymias (infrequent)

Symptoms common to both Grave's and Plummer's

65

4 tx's for hyperthyroidism

1) 131-I
2) Antithyroid drugs
3) Iodine
4) propranolol

66

MOA for 131-I

emits beta radiation, which destroys tissue in close proximity; used in output basis; carcinogenic concern, spec in kids and unborn

67

2 antithyroid drugs that are used to control hyperthyroidism until spontaneous remission. Can be used with 131-I to hasten recovery and are also used to stabilize pt until surgery

1) Methimazole (Tapazole)
2) Propylthiouracil (generic)

68

MOA of Methimazole and Propylthiouracil

1) inhibits thyroid peroxidase (blocks organification of iodide and coupling of iodotyrosine)
2) does NOT affect iodide uptake or hormone release

69

inhibits peripheral conversion of T4 to T3 by iodothyronine 5' deiodinase 1

Propylthiouracil

70

DOC for hyperthyroidism

Propylthiouracil

71

drug used in thyroid storm

propranolol

72

-beta adrenergic antagonist
-used to stabilize pt before surgery

propranolol

73

-reduces HR, tremor, palpitations, anxiety, tension

propranolol

74

Two formulations of iodine for tx of hyperthyroidism

1) Lugols (5% I1 + 10% KI)
2) Ipodate (iodinated contrast media- 61% I2)

75

MOA of iodine for tx of hyperthyroidism

-reduce vascularity of thyroid in preparation for thyroidectomy

76

MOA of cyanide

-poisons the Na/K ATPase that transports I into the cell

77

MOA of PTU and glucocorticoids

inhibit deiodination of T4 --> T3

78

what does high doses of iodide do?

inhibits T4/T3 release, inhibits organification of iodine and inhibits coupling of iodotyrosine

79

inhibition of beta blockers for hyperthyroidism

block symptomatic sites

80

site of inhibition for thioamides

-block oxidation of iodide to molecular iodine
-block coupling of iodotyrosine