LMP301 Lecture 8: Thyroid Disease Flashcards Preview

LMP301 > LMP301 Lecture 8: Thyroid Disease > Flashcards

Flashcards in LMP301 Lecture 8: Thyroid Disease Deck (82)
1

What is symptom of goiter?

Enlarged thyroid gland

2

Is goiter due to hypo, hyper, or eu-thyroid?

Can be anything

3

Goiter is due to...

Lack of iodine

4

Thyroid gland secretes...

T3 and T4

5

What is more abundant in the blood, T3 or T4?

T4

6

What makes 2/3 of the circulating T3?

Peripheral tissues (liver, kidney) deiodinate T4

7

What stimulates the production of thyroid hormones?

TSH

8

What is more biologically active, T3 or T4?

T3

9

What is the inactive form of T3?

rT3 (reverse)

10

How is rT3 produced

metabolised from T4
(T4 can make both T3 and rT3)

11

How can local thyroid status be modulated?

Balance production of T3 and rT3

12

Thyroid hormones are needed for...

all tissue maturation and metabolism

13

Precursor for thyroid hormones

tyrosine

14

MIT structure

1 iodide attached to tyrosine

15

DIT structure

2 iodides attached to tyrosine

16

T4 is made up of

DIT + DIT

17

T3 is made up of...

MIT + DIT
T4 - 1 iodine (at first benzene)

18

rT3 is made up of...

T4 - 1 iodine (at second benzene)

19

T4 is also called...

thyroxine

20

Hypothalamus-pituitary-thyroid axis for T3, T4 control

Hypothalamus: TRH
a. pituitary: TSH
Thyroid: TSH binds on TSH receptor -> T4 and T3 production

21

Feedback of thyroid hormones

TSH neg feedback on hypothalamus (short loop feedback)

T4 + T3 neg feedback on hypothalamus, a. pituitary (long loop feedback)

22

How do thyroid hormones travel? Give some examples.

Bound to carrier proteins in plasma (e.g. albumin, TBG)

23

TBG

T4-binding globulin

24

Which thyroid hormones are active?

The ones not bounded to carrier proteins in the plasma

25

% of free T3 + T4

T3: 0.3% of all T3
T4: 0.03% of all T4

26

What may change the concentration of free thyroid hormones?

Changes in the [ ] or affinity of carrier proteins

27

Are FT3 + FT4 better or worse markers of thyroid function? Why?

Better

28

Effects of increasing TBG

More T4 + T3
Same FT4
Same TSH

29

What compounds increase TBG?

- estrogen
- oral contraceptives

30

Effects of decreasing TBG

Less T4 + T3
Same FT4
Same TSH

31

Effect of inhibiting binding of thyroid hormones to TBG

Less T4
Same FT4

32

What compounds decrease TBG?

- androgens
- glucocorticoids

33

What compounds inhibit thyroid hormones from binding to TBG?

Salicylates

34

Myxedema

Dry, waxy swelling of the skin with abnormal deposits of glucosaminoglycans

35

Glucosaminoglycans

unbranched polysaccharides

36

What is myxedema a strong indication of?

hypothyroidism

37

key symptoms of hypothyroidism

- Weight gain
- fatigue
- myxedema
- high cholesterol
- slow HR

38

Hypothyroidism is a _____ syndrome

hypometabolic

39

What do thyroid hormones control in the body?

metabolism

40

Why is a symptom of hypothyroidisms high cholesterol?

Less LDL receptors produced, so less liver uptake

41

Types of hypothyroidism

1. Primary hypothyroidism
2. Secondary hypothyroidism
3. Tertiary hypothyroidism

42

Primary hypothyroidism

Problem at thyroid gland

43

Examples of problems at the thyroid gland

- autoimmune destruction (Hashimoto's disease)
- iodine deficiency
- treatment of hyperthyrodism
- congenital defects in hormone
- antithyroid drugs (side effect of some drug therapy)

44

Secondary hypothyroidism

Problems at pituitary gland (TSH)

45

Tertiary hypothyroidism

Problems at the hypothalamus (TRH)

46

Diagnosis for hypothyroidism:
High/normal TSH
High fT4

not hypothyroidism

47

Diagnosis for hypothyroidism:
High TSH
Low fT4

Primary hypothyroidism

48

What feature must be present for actual hypothyrodism to be diagnosed?

low fT4

49

Diagnosis for hypothyroidism:
High TSH
Normal fT4

subclinical hypothyrodism (high risk, but not yet hypo)

50

Diagnosis for hypothyroidism:
Low/normal TSH
Low fT4

Secondary hypothyrodism

51

Complications of hypothyroidism vary depending on...

When during the lifetime patient has the disease

52

Complications of hypothyroidism:
Pregnancy

Affect fetal development (irreversible)

53

Complications of hypothyroidism:
Infancy, childhood

- bad brain development
- can't grow tall
- low IQ
- bad psychomotor development
- cretinism (if severe)

54

Complications of hypothyroidism:
Adult

- death from myxedema coma (if severe)

55

Myxedema coma

- long-term hypothyrodism + another factor
- cold body (<80 F)
- loss of consciousness

56

Creatinism is ____ ___thyroidism

congenital
hypo-

57

Creatinism can be caused by...

- absence of thyroid gland
- thyroid hormone synthesis defects

58

Is creatinism fatal?

No
- Creatinism happens if diagnosed too late
- Early diagnosis can completely reverse effect

59

Symptoms of creatinism

- mental retardation
- short
- deaf
- neurological problems
- tongue sticking out
- flat nose bridge

60

How to treat creatinism?

replacement thyroid hormone

61

Diagnosis of creatinism

screening tests for newborns (can't usually tell from clinical symptoms)
- Screen TSH (should be high if T3 + T4 is low)
- High TSH = creatinism

62

Treatment for primary hypothyrodism

Replacement therapy with synthetic T3 + T4
- Monitor by observing TSH levels after a few weeks (should be normal)

63

Key symptoms of hyperthyrodism

- Weight loss
- Fatigue
- Glucose intolerance
- Tremor
- Infected eye
- Sweating
- Rapid heart rate
- High BP

64

Why is weight loss a symptom of hyperthyroidism?

Too much metabolic activity

65

Why is fatigue a symptom of hyperthyroidism? Why is it a symptom of hypothyrodism?

Hyper: high metabolic activity cause muscle overwork
Hypo: hormones not available, so no stimulation for metabolism

66

Causes of hyperthyrodism

1. Graves' disease
2. Plummer's disease
3. Thyroid tumour
4. Thyroiditis
5. Pituitary tumour
6. HCG secreting trophoblastic tumour
7. Iodine / iodine drugs
8. Excessive T4 + T3

67

Plummer's disease

toxic multinodular goiter:
excess production of thyroid hormones from functionally autonomous thyroid nodules

68

Graves' disease

Diffuse toxic hyperplasia:
- Autoimmune disease that affects the thyroid
- Antibodies bind to TSH receptor

69

Thyroiditis

inflammation of thyroid gland

70

HCG secreting trophoblastic tumour

HCG has same a-unit as TSH, so during prenancy, the excess HCG might bind to TSH receptor and stimulate T3 + T4 production

71

Why might high iodine cause hyperthyroidism

Iodine is a substrate needed to make T3 and T4

72

Symptoms of Grave's disease

- retracted eyelids

73

Diagnosis of Graves' disease

- Very low TSH
- Very high fT4
- Anti-TSH receptor antibodies
- Radionucleotide uptake and scan (will accumulate in the thyroid)

74

Treatment for Graves' disease

- Antithyroid drugs
- radioiodine / radiosodium (destroy thyroid gland)
- surgery to remove thyroid gland

75

Antithyroid drugs

- Block iodide uptake
- inhibit T4 synthesis
- inhibit T4 -> T3 conversion

76

Diagnosis for hyperthyroidism:
Normal TSH
Normal fT4

not thyrotoxicosis

77

Diagnosis for hyperthyroidism:
High / normal TSH
High fT4

Pituitary tumour
Thyroid hormone resistance syndrome

78

Diagnosis for hyperthyroidism:
Low TSH
Normal fT4
Normal fT3

subclinical thyrotoxicosis

79

Diagnosis for hyperthyroidism:
Low TSH
Normal fT4
High fT3

T3 toxicosis

80

Diagnosis for hyperthyroidism:
Low TSH
High fT4
T3 toxicosis

Primary thyrotoxicosis

81

thyrotoxicosis

hyperthyroidism

82

Why is glucose intolerance a symptom of hyperthyroidism?

Insulin is quickly cleared due to high metabolic rate