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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
Increased TBG blood levels along with decreased T3 resin uptake is seen in what condition?
Pregnancy
26
What happens to the thyroid hormones during hepatic failure?
Increase in free T3, T4 resulting in inhibition of synthesis for new T3 and T4 (negative feedback)
27
What happens to the thyroid hormones during pregnancy?
Increase in bound T3, T4 and decrease in free T3, T4 resulting in an increase synthesis of T3, T4
28
What hormone regulates the growth of the thyroid gland and secretion of thyroid hormones?
TSH
29
What regulates TSH?
TRH and free T3
30
What is the secondary messenger for TSH?
cAMP
31
Increased TBG levels such as during pregnancy has what effect on thyroid hormone secretion?
Stimulatory
32
Iodide deficiency has what effect on thyroid hormone secretion?
Inhibitory
33
Deiodinase deficiency has what effect on thyroid hormone secretion?
Inhibitory
34
Excessive Iodine intake (Wolff-Chaikoff effect) has what effect on thyroid hormone secretion?
Inhibitory
35
Perchlorate, thiocyanate (inhibit sodium iodide cotransport) has what effect on thyroid hormone secretion?
Inhibitory
36
Propylthiouracil (PTU) has what effect on thyroid hormone secretion?
Inhibitory
37
Decreased TBG levels seen in liver disease has what effect on thyroid hormone secretion?
Inhibitory
38
What accounts for most of the increase in metabolic rate due to its actions leading to an increase in oxygen consumption and heat production?
Increase activity of sodium potassium ATPase
39
How does hyperthyroidism affect the BMR?
Elevates it
40
How does hypothyroidism affect the BMR?
Lowers it
41
In hypothyroidism, what is the concentration of blood cholesterol?
Elevated
42
Blindness and yellowing of the skin is often seen in what patients?
Hypothyroid patients
43
What is the cardiovascular effects of thyroid hormones?
Increase in cardiac output
44
When thyroid hormone levels are high, the myocardium has increased numbers of?
Beta 1 receptors
45
When the myocardium has increased numbers of Beta 1 receptors, it is more sensitive to stimulation by?
Sympathetic nervous system
46
Thyroid hormones act synergistically with growth hormone and somatomedins to promote?
Bone formation
47
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?
Cretinism
48
In metabolism, what are the levels of thyroid hormones when there is heat intolerance, weight loss, and increase in BMR?
Excess
49
In metabolism, what are the levels of thyroid hormones when there is cold intolerance, weight gain, and decrease in BMR?
Deficient
50
In the bone, what are the levels of thyroid hormones during osteoporosis?
Excess
51
In the bone, what are the levels of thyroid hormones during stunted growth?
Deficient
52
In the CNS, what are the levels of thyroid hormones during agitation, anxiety, difficulty concentration, and hyperreflexia?
Excess
53
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?
Deficient
54
In the skin, what are the levels of thyroid hormones during sweating?
Excess
55
In the skin, what are the levels of thyroid hormones when it is dry and myxedema?
Deficient
56
In the CV system, what are the levels of thyroid hormones during tachycardia, atrial fibrillation, palpitations, and high output heart failure?
Excess
57
In the CV system, what are the levels of thyroid hormones during bradycardia, decreased contractility, and decreased cardiac output heart failure?
Deficient
58
In the intestine, what are the levels of thyroid hormones during diarrhea?
Excess
59
In the intestine, what are the levels of thyroid hormones during constipation?
Deficient
60
Thyrotoxicosis is related to what condition?
Hyperthyroidism
61
What is the most common cause of thyrotoxicosis (primary hyperthyroidism)?
Grave's disease
62
What is an example of secondary hyperthyroidism?
TSH secreting pituitary
63
What are the TSH levels during hyperthyroidism?
Decreased
64
TSH levels are decreased in hyperthyroidism due to?
Negative feedback of T3 on anterior pituitary
65
In hyperthyroidism, if the defect is in the anterior pituitary then what are the TSH levels?
Increased
66
Thyroid-stimulating immunoglobulins stimulate TSH receptor without a TSH hormone during what condition?
Grave's disease
67
What are the major clinical signs of Graves' disease?
1) Exophthalmos (abnormal protrusion of eyeball) | 2) Periorbital edema
68
How is Grave's disease diagnosed?
Elevated free T4 or T3 along with goiter
69
What helps distinguish between Grave's disease from adenoma of pituitary thyrotrophs?
Presence of circulating thyroid stimulating immunoglobulins
70
What is the most common cause of hypothyroidism in iodine-sufficient areas of the world?
Hashimoto's thyroiditis
71
What is the primary cause of hypothyroidism?
Gland destruction
72
What is the treatment of hypothyroidism?
Replacement doses of T4
73
In treatment of hypothyroidism, why are higher doses required in younger patients?
Bc metabolism of T4 decreases and plasma half-life increases with age
74
In women beyond menopause over prescribing T4 can contribute to?
Osteoporosis
75
In hashimoto's thyroiditis, decreased T3, T4 secretion is caused by?
Thyroglobulin or TPO Abs
76
In hashimoto's thyroiditis, TSH levels are? | Leading to?
1) High | 2) Goiter
77
Iodide deficiency, maternal intake of anti-thyroid medication, impaired development of thyroid gland, and inherent deficit in the synthesis of thyroid hormones leads to?
Congenital hypothyroidism
78
Untreated postnatal hypothyroidism leads to?
Cretinism
79
With a goiter, what determines whether the patient is asymptomatic or if they exhibit hypothyroidism?
Whether or not they can maintain normal blood levels of thyroid hormones
80
Postpartum hypopituitarism due to necrosis of the pituitary gland is seen in what condition?
Sheehan syndrome
81
Most patients present with galactorrhea, difficulty lactating, amenorrhea and some present with hypothyroidism in what condition?
Sheehan syndrome
82
What does the patient have if they present with decreased TSH, increased T3/T4, positive TSI, and increased radioactive iodine uptake test?
Grave's
83
What does the patient have if they present with decreased TSH, increased T3/T4, negative TSI, and decreased radioactive iodine uptake test?
Thyroiditis with hyperthyroidism
84
What does the patient have if they present with decreased TSH, increased T3/T4, negative TSI, and increased or normal radioactive iodine uptake test?
Thryoid nodule
85
What does the patient have if they present with increased TSH, decreased or normal T3/T4, and a positive antithyroid Ab?
Hashimoto's disease (early stage)
86
What does the patient have if they present with increased TSH, decreased T3/T4, and a positive antithyroid Ab?
Hashimoto's disease (later stage)
87
What does the patient have if they present with decreased TSH, decreased T3/T4, and a negative antithyroid Ab?
Pituitary abnormality

NE Exam 3 (20 decks)

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