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NE Exam 3 > Thyroid gland Physiology > Flashcards

Thyroid gland Physiology Flashcards

1
Q

What is the follicular lumen filled with?

A

Colloid

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2
Q

What are C cells (parafollicular cells) secrete?

A

Calcitonin

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3
Q

Colloid is composed of newly synthesized thyroid hormones attached to?

A

Thyroglobulin

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4
Q

Hormones stored as iodinated thyroglobulin in the follicular colloid last in the body for?

A

2-3 months

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5
Q

What hormone of the thyroid gland is 10 times more produced than its counterpart and is the major secretory product?

A

T4

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6
Q

Majority of the production of T3 comes from?

A

Peripheral conversion of T4 to T3

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7
Q

Peripheral conversion of T4 to T3 occurs through the action of?

A

Deiodinase

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8
Q

Fasting, medical/surgical stress, and catabolic diseases are some clinical states associated with?

A

Reduction in the conversion of T4 into T3

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9
Q

When the availability of iodide is restricted, the formation of what hormone is favored?

A

T3

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10
Q

Deficiency of deiodinase mimics?

A

Dietary Iodide deficiency

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11
Q

In relation to the synthesis of thyroid hormones, what is a chloride/iodide pump that is located in the apical membrane?

A

Pendrin

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12
Q

Mutation in the Pendrin gene (SLC26A4, aka PDS) causes defects in?

A

1) Transport across apical membrane

2) Cochlea (sensorineural hearing loss)

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13
Q

Patients with Pendred syndrome usually have?

A

Hypothyroidism with goiter

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14
Q

Propylthiouracil (PTU) is an effective treatment for?

A

Hyperthyroidism

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15
Q

High levels of iodide inhibit organification and synthesis of thyroid hormones, this is known as?

A

Wolff-Chaikoff effect

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16
Q

Most T3 and T4 are bound to what binding protein?

A

Thyroxine-binding globulin (TBG)

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17
Q

Where is Thyroxine-binding globulin (TBG) synthesized in?

A

Liver

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18
Q

What does Thyroxine-binding globulin (TBG) have a higher affinity for?

A

T4

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19
Q

Circulating levels of TBG can be indirectly assessed with?

A

T3 resin uptake test

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20
Q

Elevated T4 blood levels along with elevated T3 resin uptake is seen in what condition?

A

Hyperthyroidism

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21
Q

Decreased T4 blood levels along with decreased T3 resin uptake is seen in what condition?

A

Hypothyroidism

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22
Q

Elevated T4 levels and decreased T3 resin uptake are seen when TBG levels are?

A

High

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23
Q

Decreased T4 levels and increased T3 resin uptake are seen when TBG levels are?

A

Low

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24
Q

Decreased TBG blood levels along with increased T3 resin uptake is seen in what condition?

A

Hepatic failure

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25
Q

Increased TBG blood levels along with decreased T3 resin uptake is seen in what condition?

A

Pregnancy

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26
Q

What happens to the thyroid hormones during hepatic failure?

A

Increase in free T3, T4 resulting in inhibition of synthesis for new T3 and T4 (negative feedback)

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27
Q

What happens to the thyroid hormones during pregnancy?

A

Increase in bound T3, T4 and decrease in free T3, T4 resulting in an increase synthesis of T3, T4

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28
Q

What hormone regulates the growth of the thyroid gland and secretion of thyroid hormones?

A

TSH

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29
Q

What regulates TSH?

A

TRH and free T3

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30
Q

What is the secondary messenger for TSH?

A

cAMP

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31
Q

Increased TBG levels such as during pregnancy has what effect on thyroid hormone secretion?

A

Stimulatory

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32
Q

Iodide deficiency has what effect on thyroid hormone secretion?

A

Inhibitory

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33
Q

Deiodinase deficiency has what effect on thyroid hormone secretion?

A

Inhibitory

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34
Q

Excessive Iodine intake (Wolff-Chaikoff effect) has what effect on thyroid hormone secretion?

A

Inhibitory

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35
Q

Perchlorate, thiocyanate (inhibit sodium iodide cotransport) has what effect on thyroid hormone secretion?

A

Inhibitory

36
Q

Propylthiouracil (PTU) has what effect on thyroid hormone secretion?

A

Inhibitory

37
Q

Decreased TBG levels seen in liver disease has what effect on thyroid hormone secretion?

A

Inhibitory

38
Q

What accounts for most of the increase in metabolic rate due to its actions leading to an increase in oxygen consumption and heat production?

A

Increase activity of sodium potassium ATPase

39
Q

How does hyperthyroidism affect the BMR?

A

Elevates it

40
Q

How does hypothyroidism affect the BMR?

A

Lowers it

41
Q

In hypothyroidism, what is the concentration of blood cholesterol?

A

Elevated

42
Q

Blindness and yellowing of the skin is often seen in what patients?

A

Hypothyroid patients

43
Q

What is the cardiovascular effects of thyroid hormones?

A

Increase in cardiac output

44
Q

When thyroid hormone levels are high, the myocardium has increased numbers of?

A

Beta 1 receptors

45
Q

When the myocardium has increased numbers of Beta 1 receptors, it is more sensitive to stimulation by?

A

Sympathetic nervous system

46
Q

Thyroid hormones act synergistically with growth hormone and somatomedins to promote?

A

Bone formation

47
Q

Neural changes induced by thyroid hormone deficiency during the perinatal period are irreversible and lead to what unless replacement therapy is started soon after birth?

A

Cretinism

48
Q

In metabolism, what are the levels of thyroid hormones when there is heat intolerance, weight loss, and increase in BMR?

A

Excess

49
Q

In metabolism, what are the levels of thyroid hormones when there is cold intolerance, weight gain, and decrease in BMR?

A

Deficient

50
Q

In the bone, what are the levels of thyroid hormones during osteoporosis?

A

Excess

51
Q

In the bone, what are the levels of thyroid hormones during stunted growth?

A

Deficient

52
Q

In the CNS, what are the levels of thyroid hormones during agitation, anxiety, difficulty concentration, and hyperreflexia?

A

Excess

53
Q

In the CNS, what are the levels of thyroid hormones with cretinism (congenital) or in adults with listlessness, slowed movement, somnolence, impaired memory, and decreased mental capacity?

A

Deficient

54
Q

In the skin, what are the levels of thyroid hormones during sweating?

A

Excess

55
Q

In the skin, what are the levels of thyroid hormones when it is dry and myxedema?

A

Deficient

56
Q

In the CV system, what are the levels of thyroid hormones during tachycardia, atrial fibrillation, palpitations, and high output heart failure?

A

Excess

57
Q

In the CV system, what are the levels of thyroid hormones during bradycardia, decreased contractility, and decreased cardiac output heart failure?

A

Deficient

58
Q

In the intestine, what are the levels of thyroid hormones during diarrhea?

A

Excess

59
Q

In the intestine, what are the levels of thyroid hormones during constipation?

A

Deficient

60
Q

Thyrotoxicosis is related to what condition?

A

Hyperthyroidism

61
Q

What is the most common cause of thyrotoxicosis (primary hyperthyroidism)?

A

Grave’s disease

62
Q

What is an example of secondary hyperthyroidism?

A

TSH secreting pituitary

63
Q

What are the TSH levels during hyperthyroidism?

A

Decreased

64
Q

TSH levels are decreased in hyperthyroidism due to?

A

Negative feedback of T3 on anterior pituitary

65
Q

In hyperthyroidism, if the defect is in the anterior pituitary then what are the TSH levels?

A

Increased

66
Q

Thyroid-stimulating immunoglobulins stimulate TSH receptor without a TSH hormone during what condition?

A

Grave’s disease

67
Q

What are the major clinical signs of Graves’ disease?

A

1) Exophthalmos (abnormal protrusion of eyeball)

2) Periorbital edema

68
Q

How is Grave’s disease diagnosed?

A

Elevated free T4 or T3 along with goiter

69
Q

What helps distinguish between Grave’s disease from adenoma of pituitary thyrotrophs?

A

Presence of circulating thyroid stimulating immunoglobulins

70
Q

What is the most common cause of hypothyroidism in iodine-sufficient areas of the world?

A

Hashimoto’s thyroiditis

71
Q

What is the primary cause of hypothyroidism?

A

Gland destruction

72
Q

What is the treatment of hypothyroidism?

A

Replacement doses of T4

73
Q

In treatment of hypothyroidism, why are higher doses required in younger patients?

A

Bc metabolism of T4 decreases and plasma half-life increases with age

74
Q

In women beyond menopause over prescribing T4 can contribute to?

A

Osteoporosis

75
Q

In hashimoto’s thyroiditis, decreased T3, T4 secretion is caused by?

A

Thyroglobulin or TPO Abs

76
Q

In hashimoto’s thyroiditis, TSH levels are?

Leading to?

A

1) High

2) Goiter

77
Q

Iodide deficiency, maternal intake of anti-thyroid medication, impaired development of thyroid gland, and inherent deficit in the synthesis of thyroid hormones leads to?

A

Congenital hypothyroidism

78
Q

Untreated postnatal hypothyroidism leads to?

A

Cretinism

79
Q

With a goiter, what determines whether the patient is asymptomatic or if they exhibit hypothyroidism?

A

Whether or not they can maintain normal blood levels of thyroid hormones

80
Q

Postpartum hypopituitarism due to necrosis of the pituitary gland is seen in what condition?

A

Sheehan syndrome

81
Q

Most patients present with galactorrhea, difficulty lactating, amenorrhea and some present with hypothyroidism in what condition?

A

Sheehan syndrome

82
Q

What does the patient have if they present with decreased TSH, increased T3/T4, positive TSI, and increased radioactive iodine uptake test?

A

Grave’s

83
Q

What does the patient have if they present with decreased TSH, increased T3/T4, negative TSI, and decreased radioactive iodine uptake test?

A

Thyroiditis with hyperthyroidism

84
Q

What does the patient have if they present with decreased TSH, increased T3/T4, negative TSI, and increased or normal radioactive iodine uptake test?

A

Thryoid nodule

85
Q

What does the patient have if they present with increased TSH, decreased or normal T3/T4, and a positive antithyroid Ab?

A

Hashimoto’s disease (early stage)

86
Q

What does the patient have if they present with increased TSH, decreased T3/T4, and a positive antithyroid Ab?

A

Hashimoto’s disease (later stage)

87
Q

What does the patient have if they present with decreased TSH, decreased T3/T4, and a negative antithyroid Ab?

A

Pituitary abnormality

NE Exam 3 (20 decks)

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