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Endocrinology - Chapters > Chapter 66 > Flashcards

Chapter 66 Flashcards

1
Q

The thyroid gland secretes ____ and _____, both of which modulate energy utilization and heat production and facilitate growth.

A

thyroxine (T4)

triiodothyronine (T3)

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2
Q

The follicular cells of the thyroid synthesize ______ which is then stored as colloid.

A

thyroglobulin

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3
Q

Biosynthesis of T3 and T4 occurs by iodination of?

A

tyrosine molecules in thyroglobulin

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4
Q

______ is essential for the synthesis of thyroid hormones.

A

Dietary iodine

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5
Q

Iodide is enzymatically oxidized by ________ _______ which also mediates the ionization of the tyrosine residues in thryoglobin to form monoiodotyrosine and diiodotyrosine.

A

thyroid peroxidase

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6
Q

________ molecules couple to form T3 and T4.

A

Iodotyrosine molecules

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7
Q

Secretion of free T3 and T4 into the circulation occurs after proteolytic digestion of ______ which is stimulated by _______.

A

thyroglobulin

TSH

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8
Q

T4 and T3 are tightly bound to these serum carrier proteins (3)

A

thyroxine-binding globulin (TBG)
thryroxine-binding prealbumin
albumin

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9
Q

The unbound or free fractions of T4 and T3 are the biologically (active or inactive?) fractions and represent only 0.04% of the total T4 and 0.4% of the total T3.

A

active

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10
Q

The normal thyroid gland secretes T4, T3 and _____, a biologically inactive form of T3.

A

reverse T3

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11
Q

T3 is derived from?

A

5’-deiodination of circulating T4 in peripheral tissues

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12
Q

Deionization of T4 can occur at the _____ ring, producing T3, or at the ______ ring, producing reverse T3.

A

outer ring- T3

inner ring- reverse T3

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13
Q

Hypothalamic thyrotropin releasing hormone (TRH) is transported through the ____________ to the thyrotrophs of the anterior pituitary gland where they stimulate synthesis and release of _______.

A

hypothalamic-hypophysial portal system

TSH

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14
Q

____ increases thyroidal iodide uptake and iodination of thyroglobin.

A

TSH

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15
Q

____ releases T3 and T4 from the thyroid gland by increasing ______ of thyroglobulin and stimulates cell growth.

A

TSH

Hydrolysis

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16
Q

Hypersecretion of TSH results in _______ _________.

A

Thyroid enlargement (goiter)

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17
Q

Circulating ___ exerts negative feedback inhibition of TRH and TSH release.

A

T3

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18
Q

Thyroid hormones increase basal metabolic rate by increasing ________ and _______ in several body tissues.

A

Oxygen consumption

Heat production

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19
Q

Thyroid gland function and structure can be evaluated by what 4 things?

A

determining serum hormone levels
imaging thyroid gland size and architecture
measuring thyroid antibodies
FNA

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20
Q

Total serum T4 and T3 measure the total amount of hormone bound to thyroid binding proteins by _________

A

radioimmunoassay

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21
Q

Total T4 and T3 levels are elevated in ___________.

A

hyperthyroidism

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22
Q

Total T4 and T3 levels are low in ___________.

A

hypothyroidism

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23
Q

Increase in _____ as with pregnancy or estrogen therapy, increases the total T4 and T3 without actual hyperthyroidism.

A

TBG

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24
Q

Free T4 levels are usually measured by…

A

measured directly
dialysis
ultrafiltration

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25
Q

Serum TSH is measure by ________ which uses at least two different monoclonal antibodies against different regions of the TSH molecule- allows for accurate discrimination btwn normal levels of TSH and levels below normal.

A

third-generation immunometric assay

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26
Q

TSH assay can diagnose _________ and __________.

A

hyperthyroidism and subclinical hyperthyroidism

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27
Q

Thyroidism in which there is elevated free T4 and suppressed TSH.

A

Hyperthyroidism

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28
Q

Thyroidism in which there are normal free T4 levels and supporessed TSH.

A

subclinical hyperthyoidism

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29
Q

In primary (thyroidal) hypothyroidism, serum TSH is _______ because of diminished feedback inhibition.

A

supranormal

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30
Q

In secondary (pituitary) and tertiary (hypothalamic) hypothyroidism, TSH is usually _____ but may be normal.

A

low

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31
Q

______ ______ measurements are useful in the followup of patients with papillary or follicular carcinoma.

A

serum thyroglobulin

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32
Q

After thyroidectomy and iodine-131 ablation therapy, thyroglobin levels should be less than _____ while the pt is on suppressive levothyroxine treatment- levels higher than this suggest persistent or metastatic disease.

A

0.5 mcg/L

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33
Q

Calcitonin is produced by _____ of the thyroid and has a minor role in calcium homeostasis

A

C-cells

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34
Q

Calcitonin meausrements are invaluable in the diagnosis of ________ ________ of the thyroid and for monitoring the effects of therapy.

A

medullary carcinomas

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35
Q

In thyroid imaging, ________ is concentrated in the thyroid gland and can be scanned with a gamma camera, yielding info about the size and shape and the location of the functional activity in the gland.

A

technetium-99m pertechnetate

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36
Q

Which type of thyroid nodule (hot/cold) is nonfunctioning and is usually associated with malignancy?

A

cold nodule

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37
Q

________ ________ evaluation is useful in the differentiation of solid nodules from cystic nodules and can be used to guide a clinician during an FNA.

A

thyroid ultrasound

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38
Q

____ of a nodule to obtain thyroid cells for evaluation is the best way to differentiate benign from malignant disease

A

FNA- fine needle aspiration

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39
Q

________ is the clinical syndrome that results from elevated circulating thyroid hormones.

A

Thyrotoxicosis

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40
Q

Clinical manifestations of thyrotoxicosis is due to the direct physical effects of the thyroid hormones as well as the increased sensitivity to _________.

A

catecholamine

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41
Q

Tachycardia, tremor, stare, sweating, and lid lag can be seen in hyperthryodism due to?

A

catecholamine hypersensitivity

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42
Q

Thyrotoxic crisis, or thyroid storm is a life threatening complication of hyperthyroidism that can be precipitated by

A

surgery
radioactive iodine therapy
severe stress (eg uncontrolled Diabetes mellitus, myocardial infarction, acute infection)

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43
Q

What are some of the symptoms of a patient experiences a thyroid storm?

A 
fever
flushing
sweating
significant tachycardia
atrial fibrillation
cardiac failure 
significant agitation 
restlessness
delerium
N/V, diarrhea
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44
Q

What is the hallmark of a thyroid storm?

A

hyperpyrexia (abnormally high fever) of proportion to other clinical findings

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45
Q

DDx: Thyrotoxicosis usually reflects excess secretion of thyroid hormones resulting from? (4)

A 
Graves disease
toxic adenoma
mulitnodal goiter
thyroiditis 
excessive ingestion of Thyroid hormone 
Rarely-thyroid hormone production from ectopic site
46
Q

What disease is the most common cause of thyrotoxicosis? T/F: It is an autoimmune disease.

A

Graves disease

True

47
Q

What are some of the possible features present in a patient with Graves disease?

A

Goiter, thyrotoxicosis, eye disease- ranging from tearing to proptosis, extraocular muscle paralysis, loss of site, thyroid dermopathy- significant skin thickening without pitting in a pretibial distribution (pretibial myxedema)

48
Q

Thyrotoxicosis in Graves disease is due to?

A

overproduction of an antibody that binds to the TSH receptor

49
Q

How does the overproduction of the antibody that binds to the TSH receptor effect the thyroid?

A

The thyroid stimulating immunoglobulins increase thyroid cell growth and thyroid hormone secretion.

50
Q

The inflammatory reaction that contributes to the eye signs in Graves disease may be caused by _______ sensitized to antigens common to the oribital muscles and thyroid.

A

lymphocytes

51
Q

The common manifestations of thyrotoxicosis are characteristic features of (younger or older?) with ________ disease, a diffuse _______ or the ____ signs, characteristic of Graves.

A

younger
Graves
goiter
eye signs

52
Q

Older patients often do not have the florid clinical features of thyrotoxicosis, and the condition is termed ________ __________.

A

apathetic hyperthyroidism

53
Q

What are a few clinical features of an older patient experiencing apathetic hyperthyroidism?

A

flat effect, emotional lability, weight loss, muscle weakness, congestive heart failure and atrial fib resistant to standard therapy

54
Q

What are some of the possible effects of Graves disease on the eyes?

A

peroribial edema, conjunctival congestion, swelling, proptosis, extraocular muscle weakness, or optic nerve damage with visual impairment

55
Q

What is a clinical manifestation of Graves that is characterized by skin thickening of the skin over the lower tibia without pitting?

A

pretibial myxedema

56
Q

Which nail diseases are often found in patients with Graves?

A

onycholysis–seperation of of the fingernails from their nail beds
thryoid acropachy- clubbing

57
Q

How do the levels of T4, T3 and TSH present in patients with thyrotoxicosis?

A

T4 and/or T3 are elevated and TSH is suppressed.

58
Q

Thyroid stimulating immunoglobulin is usually elevated in thyrotoxicosis and may be useful in which patients?

A

Patients with eye signs who do not have other characteristic clincial features

59
Q

What is a differential factor of Graves disease from EARLY SUBACUTE Hashimoto thyroiditis in lab findings?

A

There is an increased uptake of 123I in Graves disease- uptake is low in presence of

60
Q

What are the two commonly used imaging techniques used to view the orbital muscles for possible enlargement, or signs of ophthalmopathy?

A

MRI

ultrasonography

61
Q

What are the three treatment modalities used to control the hyperthyroidism of Graves?

A

antithyroid drugs
radioactive iodine
surgery

62
Q

The thiocarbamide drugs (antithyroid drugs) _______, _______ and ______ block thyroid hormone synthesis by inhibiting thyroid peroxidase.

A

proplythiouracil
methimazole
carbimazole

63
Q

Which antithyroid drug partially inhibits peripheral conversion of T4 to T3?

A

propylthiouracil

64
Q

When treating hyperthyroidism with medical therapy, it must be administered for how long?

A

a prolonged period (1-2 years) or until the disease undergoes spontaneous remission

65
Q

Patients who experience relapse of hyperthyroidism after medical therapy must undergo…

A

definitive surgery

radioactive iodine treatment

66
Q

What are side effects of using thiocarbamide drugs to treat hyperthyroidism?

A

pruritis and rash
cholestatic jaundice
acute arthralgias (joint pain)
rarely- agranulocytosis (low levels of WBCs)

67
Q

Patients may be instructed to discontinue medical therapy if sore throat or fever develops because these symptoms indicate _________.

A

agranulocytosis

68
Q

At the onset of treatment, during the acute phase of thyrotoxicosis, _________ drugs help alleviate tachycardia, hypertension, and atrial fibrillation.

A

beta adrenergic blocking drugs

69
Q

In terms of cost, efficacy, ease and short term side effects, radioactive iodine has greater benefits than surgery or antithyroid drugs. Down side: what usually develops after use?

A

Most patients become hypothyroid following its use.

70
Q

What is often the treatment of choice in adults with Graves disease but is contraindicated in pregnant women?

A

131^I (to clarify, superscript 131 I )

71
Q

What should be done differently in pts with severe thyrotoxicosis, very large glands or underlying heart disease when being treated with radioactive iodine (131I)?

A

They should be rendered euthyroid (normal thyroid function) with antithyroid medication before receiving radioactive iodine.

72
Q

Why is it important for normal thyroid function to be obtained before treatment with radioactive iodine (131I) in patients withsevere thyrotoxicosis, very large glands or underlying heart disease?

A

It can cause a release of preformed thyroid hormone from thyroid hormone into circulation which can cause cardiac arrythmias and worsen the symptoms of thyrotoxicosis.

73
Q

After administering radioactive iodine, the thyroid shrinks and patients become euthyroid over a periods of?

A

6 weeks to 3 months

74
Q

What levels should be monitored when treatment with radioactive iodine is used? What can be given if hypthyroidism occurs?

A

Serum free T4 and TSH levels

levothyroxine

75
Q

When does hypothyroidism occur in patients after being treated for hyperthyroidism?

A

ALWAYS- total thyroidectomy
frequently- subtotal thyroidectomy
smaller %- txt with antithyroid medications

76
Q

For patients with very large glands and obstructive symptoms, multi nodular glands or for patients desiring pregnancy in the next year, what is the treatment of choice?

A

total or subtotal thyroidectomy

77
Q

Before a thyroidectomy, patients must do what?

A

Receive antithyroid drugs for SIX WEEKS- to ensure euthyroid, and take oral saturation solution of potassium iodide daily for TWO WEEKS prior- to decrease vascularity of the gland

78
Q

Solitary, toxic nodules (usually benign) occur more frequently in (older or younger?) patients.

A

older

79
Q

Clinical manifestations of toxic adenomas are those of _______.

A

thyrotoxicosis

80
Q

Physical exam of toxic adenoma shows what type of nodule?

A

distinct solitary nodule

81
Q

What would the lab results for T4, T3 and TSH be for a patient with toxic adenomas?

A

suppressed TSH
significantly elevated T3
moderately elevated T4

82
Q

Would a toxic adenoma appear hot or cold in a thyroid scan?

A

it would show a hot nodule of the affected lobe with complete suppression of the unaffected lobe

83
Q

How are solitary toxic nodules (toxic adenoma) treated?

A

radioactive iodine

unilateral lobectomy may be required for large nodules (after rendered euthyroid by antithyroid drugs)

84
Q

_______ _________ ______ occurs in older patients especially from iodine-deficient regions who are exposed to increased dietary iodine or receive iodine-containing radiocontrast dyes.

A

toxic multinodular goiter

85
Q

Clinical presenting features in pts with a toxic multinodular goiter are?

A

tachycardia
heart failure
arrhythmias

86
Q

Diagnosis of a toxic multinodular goiter can be confirmed by these lab results for levels of TSH, T4 and T3 and a thyroid scan exhibiting what?

A

suppressed TSH
elevated T3 and T4
thyroid scan- multiple functioning nodules

87
Q

What is the treatment of choice for a toxic multinodular goiter?

A

131I ablation

88
Q

In subclinical hyperthyroidism, what are the levels of T4, T3 and TSH like?

A

T4 and T3 levels are normal

TSH levels are suppressed

89
Q

What are some of the causes of subclinical hyperthyroidism?

A

early presentation of hyperthyroidism- Graves disease, toxic adenoma, and toxic multinodular goiter

90
Q

Pts with subclinical hyperthyroidism are at a higher risk for developing ________ _______ (esp. the older pts) and many have persistently suppressed TSH and should be treated with ________ _____ or ______ ______.

A

thiocarbamide drugs

radioactive iodine

91
Q

A decrease in ______ _______ ______ is another indication for treatment for subclinical hyperthyroidism.

A

bone mineral density

92
Q

What is the initial presentation of thyroiditis?

A

often that of hyperthyroidism- result of acute release of T4 and T3

93
Q

How does thyroiditis present?

A

It initially presents as hyperthyroidism but may eventually result in clinical hypothyroidism.

94
Q

Hyperthyroidism caused by thyroiditis can be readily differentiated from other causes by?

A

suppressed uptake of radioactive iodine, reflecting decreased hormone production by damaged cells

95
Q

What is a rare type of thyroiditis in which the pt exhibits, high fever, redness of overlying skin and thyroid gland tenderness? It is often confused with subacute thyroiditis.

A

acute suppurative thyroiditis

96
Q

An acute inflammatory disorder of the thyroid gland, probably secondary to a viral inf. in which the pt complains of fever and anterior neck pain and symptoms of hyperthyoidism are present- classic feature: exquisitely tender thyroid gland

A

subacute thyroiditis

97
Q

What is the treatment for subacute thyroiditis?

A

nonsteroidal anti-inflammatory drugs and possibly prednisone if pain and fever are severe

98
Q

_________ from destruction of normal thyroidal structure by lymphocytic infiltration results in hypothyroidism and goiter.

A

chronic thyroiditis

99
Q

________ thyroiditis is more common in women and is the most common cause of goiter and hypothyroidism in the United States.

A

Hashimoto’s

100
Q

How can chronic thyroiditis be differentiated from subacute thyroiditis?

A

in chronic, the gland is nontender to palpation and antithyroid antibodies are present in high titer

101
Q

Patients with Hashimoto’s may have transient hyperthyroidism with low radioactive iodine uptake, owing to….

A

the release of T4 and T3 into the circulation

102
Q

When an FNA is taken in a patient with chronic thyroiditis, what would you expect to see?

A

lymphocytes and Hurthle cells (enlarged basophilic follicular cells)

103
Q

Hypothyroidism and significant glandular enlargement (goiter) are indications for _________ therapy.

A

levothyroxine

104
Q

______ ______ exhibits typical features of thyrotoxicosis from ingestion of excessive amounts of thyroxine, often in an attempt to lose weight.

A

thyrotoxicosis factita

105
Q

In a patient with thyrotoxicosis factita, how do the serum T4 & T3 and TSH levels present? Is radioactive iodine uptake present?

A

serum T4 & T3 levels are elevated and TSH is suppressed.. Radioactive iodine uptake is absent.

106
Q

_____ ____ occurs when an ovarian teratoma contains thyroid tissue which secretes thyroid hormone.

A

Struma ovarii

107
Q

What is the best imaging techinque to diagnose the presence of a struma ovarii?

A

a body scan demonstrating uptake of radioactive iodine in the pelvis

108
Q

_________ ____ is due to proliferation and swelling of the trophoblast during pregnancy, with excess production of chorionic gonadatropin, which has intrinsic TSH-like activity

A

hydatidiform mole

109
Q

Postpartum thyroiditis resembles ______ ________ in its clinical course and it usually occurs within the first ____ months after delivery.

A

subacute thyroiditis

6 months

110
Q

Postpartum thyroiditis goes through a triphasic course of presentation; first presenting as _______ then _________ then _______. Or it may develop with only _________. pg 674

A

1) hyperthyroidism, hypothyroidism, euthyroidism

2) hypothyroidism

Endocrinology - Chapters (20 decks)

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