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ENDOCRINE > Thyroid CHapter > Flashcards

Thyroid CHapter Flashcards

1
Q

Thyroid

A 
Micro L
Cystic 
Peripheral vascularutt
Round shape
—-
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2
Q

Type 1 deiodinase

A

Outer and inner Ring

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3
Q

Deiodinase

Subcellular location in endoplasmic reticulim

A

Type 2

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4
Q

Deiodinase

Outer ring

A

Type 2

Type 1 outer and inner

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5
Q

Deiodinase

High susceptibility to PTU

A

Type 1

Inner and outer - inhibited by PTU and activated by thyroid hormone

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6
Q

Deiodinase

Decreased response to increased T4 (the rest increases)

A

Type 2

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7
Q

Deiodinase

Source of plasma t3 in thyrotoxic patients

A

Type 3

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8
Q

Deiodinase

Found in liver kidney thyroid pituitary

A

Type 1

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9
Q

Effects of thyrotoxicosis in CV system

A

> decreased peripheral vasc resistance to dissipate heat

> inc CO inc HR inc SV

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10
Q

Mechanism of increased cardiac contractility in thyrotoxicosis

A

Increase in ratio of alpha to B myosin chain

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11
Q

Mearns Lerman scratch

A

Scratchy systolic sound in left sternal border resembling a pleuripericardial friction rub found in thyrotoxicosis

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12
Q

% of px with unexplained atrial fibrillation who are thyrotoxic

A

15%

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13
Q

Percent of px with thyroxtoxicosis who have atrial fibrillation

A

2-20%

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14
Q

Most common thyroid neoplasm

A

Follicular adenoma

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15
Q

Dose of rTSH

A

0.01 to 0.03 mg

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16
Q

TNM scoring

T4

A 
T0 no evidence of prary tumor
T1 <1 
T2 2-3
T3 4 cm limited to thyroid
T4 extending beyond the thyroid
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17
Q

Most impt cytologic variant of thyroid CA whicb composed predominantly entirely of large cells with granular eosinophilic cytoplasm

A

Oxyphilic / oncocytic/ hurthle cell adenoma

alignant

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18
Q

PTC variant with poor progmostic finding

A

Hobnail variant with micropapillary pattern

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19
Q

PTC variant cells twice as tall as they are wide

A

Tall cell variant

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20
Q

PTC variant prominent nuclear stratification of elongated cells

A

Columnar cell variant

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21
Q

Aggrassive variants

A

Tall cell

Columnar cell variant

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22
Q

Nuclear changes in FNA

A

Nuclei are larger than N folloculae cells and overlap
Fissured like coffee beans
Ground glass nuclei (Chromatin hypodense)
Contain an inclusion corresponding to cytoplasmic invagination

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23
Q

Protooncogene whose activation is found only in PTC

A

RET

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24
Q

Where is RET found

A

Chr 10q11-2

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25
Q

% of thyroid malignancies that are medullar

A

5%

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26
Q

Mutation found in tall cell bariant of PtC

A

BRAF

Associated with higher risk of recurrence

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27
Q

Age papillary thyroid CA

A

30- 50 yrs

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28
Q

Female predominance of ptca

A

80

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29
Q

FTC

A

Invasion of capsule blood vessel or adjacent thyroid

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30
Q

CA more common in areas with iosine deficiency

A

Folliculae CA

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31
Q

Oncogene in FTCs

A

RAS oncogene

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32
Q

Cytogenetic abnormality limited to FTC

A

P arm chromosome 3

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33
Q

Age anaplastic thyroid CA

A

After 60 yrs

FTC- 50 yrs ave

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34
Q

Hypothyroidism without a goiter

A

Atrophoc thyroiditis

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35
Q

Commonest cause of goiter in iodine sufficient regions

A

Hasimotos

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36
Q

Presence of this may be a favorable prognostic factor in patients with papillary CA

A

Hashimoto

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37
Q

Suspected in hashimoto px witb painful enlargement of the thyroid gland
Occurs almost exclusively in hasimoto patients

A

THYROID LYMPHOMA

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38
Q

Impairment of intrathyroidal Nd peripheral deiodination of iodotyrosines

A

Ipdotyrosine dehydrogenase defect

DEHAL1B gene

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39
Q

Unusual cause of hypothyroidism that has been identified in infants with visceral hemangiomas

A

Consumptive hypothyroidism

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40
Q

Contained in cassava

A

Linamarin

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41
Q

Tsh goal of treafment in Hashimoto

A

Tsh in the lower half of the reference interval

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42
Q

Action of lithium and why it causes hypothyroidism

A

Inhibits thyroid hormone release

In high concentrations can inhibit organic binding reactions

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43
Q

Pendred syndrome

A

Defect in iodine organificatkon and sensory nerve deafness

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44
Q

Difference in finding:

Painful versus painless subacute thyroiditis

A

Painful- small and atrophic

Painless- enlarged and dfirm infiltraion

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45
Q

% of thyroid independent of pituitary

Why central is leas severe than primary hypothyroidism

A

10-15%

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46
Q

Expressed by visceral hemangiomas

A

D3

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47
Q

Defects in this gene causes hereditary hypothyroidism

A

POUf1 Nd prop 1

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48
Q

More common type of mutation in RTH (resistance to thyroid hormone)

A

Mutation in thyroid hormone receptor B

Interferes capacity of receptor to respond normally to T3

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49
Q

Presentation of patients witb RTH

A

Mix of hyper and hypo

Palpitations and tachy
Growth retardation

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50
Q

Profile of RTH patient

A

inc ft4
N or alightly increased tsh
Tachy
Goiter

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51
Q

Treatment of RTH

A

TRIAC

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52
Q

Time required for complete equilibriation of FT4

A

6 weeks

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53
Q

% of levothyroxine absorbed in stomach

A

80%

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54
Q

Px with impaired gastric acid secretion require higher dose levothyroxine
How higher

A

22-34% higher

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55
Q

Dose adjustment thyroid hormone in Elderly because thyroid hormone clearance is decreased

A

20-30% less

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56
Q

Increase thyroid hormone requirement in pregnancy

A

First trimester

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57
Q

Reasons for the increase req of thyroid hormone in the first trimester of pregnancy

A
  • increased T4 binding
  • increased volume of distribution of T4
  • increase in D3 in placemta
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58
Q

Dose levothyroxine myxedema coma

A

Levothyroxine 500-800 IV
Then 100 IV thereafter

Hypertonic Saline!!!
IV liothyrosine 25 ug q12

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59
Q

Rx reidel thyroiditis

A

Tamoxifen

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60
Q

Acute thyroiditis VS Subacute thyroiditis

Preceding upper respiratory infection
Fever
Sorethroat

A

Acute

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61
Q

Acute thyroiditis VS Subacute thyroiditis

Paiful thyroid swelling

A

100- acute

77- subacute

62
Q

Acute thyroiditis VS Subacute thyroiditis

Left side affected

A

Acute

63
Q

Acute thyroiditis VS Subacute thyroiditis

Migratory thyroid tenderness

A

Sibacute

64
Q

Acute thyroiditis VS Subacute thyroiditis

Abnormal thyroid hormone levels
Elevated or depressed

A

Subacute

65
Q

Acute thyroiditis VS Subacute thyroiditis

FNAB
Purulent bacteria fungi

A

Acute

In subacute - lymphocytes macriphage giant cells

66
Q

Acute thyroiditis VS Subacute thyroiditis

Response to GC treatment

A

Acute transient

Subacute 100%

67
Q

Acute thyroiditis VS Subacute thyroiditis

Gallium scan positive

A

Both

68
Q

Thyroid fibrosis in middle aged women

A

Riedel chronic sclerosing thyroiditis

69
Q

Tissue location of type 1 deiodinase

A

Liver
Kidney
Thyroid
Pituitary

Type 2
Cns brown adipose tissue heart skeletal muscle placenta

Tupe 3 placenta cns hemangiomas

70
Q

Half life of T 3

A

0.75 days

71
Q

The most impt thyroid hormone inactivating emzyme

A

D3

Inner ring deiodinase

72
Q

Recommended iodine dose pregnant

A

200 ug

Adults 150 ug
Children 90-120 ug

73
Q

Naturally occuring I

A

I 127

74
Q

Suggested starting dose of MMI in the setting of AIT

Ata guidelines

A

40 mg OD

75
Q

How are T3 and T4 transported across cellular membranes

A

MCT8

MCT10

76
Q

Proteins facilitating transport of T4 and T3 across cell membranes

A

Mct8 and mct10

77
Q

Transport of T4 across blood brain barrier

A

OAYP1C1

78
Q

Mutation in the MCT8 gene

Mental retardation
Increased T3
Dysarthria
Athetoid movements

A

Allan Herndon Dudley Syndrome

79
Q

Rx for mct8 gene mutation

A 
PTU with LT4
Diiosithyropropionic acid (DITPA)
80
Q

Most impt pathway for T4 metabolism

A

Outer ring
D1 and D2

And is 80% of the source of T3 for humans

81
Q

Diff of D1 Nd d2

A

D1 hugher Km
Prefers T3 Nd T3so4
Inhibited by PTU
Increased by thyroid hormone (D2 decreased)

82
Q

To convert T4 nmol to ug/dl

A

Divide by 12.87

83
Q

Half lfe of TBG

A

5 days

84
Q

% of T3 bound by TBG

A

T3 80%

T4 64 %

85
Q

Blocks synthesis of TBG

A

L asparaginase

86
Q

Major thyroid hormone binding protein in the csf

A

Transthyretin (TTR)

Found in choroid plexus

87
Q

Moa if iopanoic and iopodipie acid

A

Inhibit deiodinases

88
Q

Iodine per drop of sski

A

38 mg/drop

Lugols 6 mg/drop

89
Q

Quantity of iodine required to supress tadioactive iodine to <2

A

> 30 mg/day

90
Q

Iodine content per iodized salt

A

760/10 g

91
Q

Iodine content angiographic and CT dyes

A

400-4000 mg/dose

92
Q

How growth hormone affects thyroud

A

Decrease D3 activity outer ring deoidination

93
Q

Biochemical markers of thyroid status

Decreased during thyrotoxicosis

A

Low low

LDL
Lipoproteins

94
Q

Biochemical markers of thyroid status

Increased during thyrotoxicosis

A 
Vw
Osteocalcin
Urine pyridium
Ferritin 
ALP
Sex hormone BG
ANP
95
Q

Decreased during hypothyroidism

A

Vassopressin

96
Q

Spared graves ophthalmoplegia

A

Muscle tendons spared

With lateral rectus least commonly affected

97
Q

10 mg carbimaxole is metabolized to ___

A

6 mg methimazole

98
Q

Multinodular toxic goiter

A

12-14 mci

99
Q

Transient thyrotoxicosis where thyroid tenderness is the most prominent symptom and thyrotoxicosis is rare

A

Viral thyroiditis
Subacute
De quervain
Granulomatous

100
Q

Histopath subacute thyroiditis/

Giant cell thyroiditis

A

Well developed follicular lesion that consists of cebtral core of colloid surrounded by multinucleated giant cells

101
Q

(+) sudden appearance of pain in region of thyroid gland wuth or without fever
Aggravated by turning head or swallowing radiates to ear and occiput

A

Subacute thyroiditis
De quercain
Granulomayous
Giant cell

102
Q

Viral infection of thyroid gland preceded by URTI

A

Subacute thyroiditis

103
Q

Differentiate acute exacerbation if hasgimito thyroiditis and de quervain/ subacute thyroiditus

A

Lack of elecation if ESR in hasimotis

104
Q

Rx compromised Cv function hypothyroid

A

DITPA

105
Q

Acute thyroiditis commonly affects which lobe

A

Left lobe

106
Q

1 mCi= __ MBq

A

37

107
Q

Preferred substrate of D1

A

rT3

T3 SO4

108
Q

An excess of thyroid hormone increases this deiodinase

A

D1

D2- reduced by thyroid hormones

109
Q

Deiodinase with Half life of 20-30 mins

A

D2

D1 and D3 has long half life (more than 12 hrs)

110
Q

Source of TRH

A

Parvocellular region of paracentricular nuclei

111
Q

Hormone picture of thyroid hormone resistance

A

Elevated FT4 ans TSH

112
Q

Enzyme in the CNS that rapidly degrades TRH

A

protein peptidase II

  • exclusively !
113
Q

Riedel’s thyroiditis may be treated with this drug

A

Tamoxifen

114
Q

How does somatostatin affect TSH secretion

A

Inhibits TSH
So does:
- Dopamine
- Bromocriptine (dopamine agonist)

115
Q

Half life of TSH

A

30 mins

116
Q

Is FT3 the only one capable of activating thyroid hormone receptors thats why it is called the active thyroid hormone?

A

Nope, however it binds TRs with 15x affinity compared to FT4 explaining its function as the active thyroid hormone

117
Q

Iodine per drop of lugols

A

6 mg/ drop

118
Q

Iodine per tab of amiodarone

A

75-200 mg

119
Q

Iodine in prenatal vitamins

A

150 ug/tab

120
Q

Responsible for the escape / adaptation phenomenon in wolf chaikoff

A

Decrease in NIS expression causing decrease in iodide transport activity

121
Q

Why should chronic high iodine intake during pregnancy be avoided?

A

The escape phenomenon does not occur in the 3rd trimester fetus—> hypothyroidism

122
Q

Daily iodine requirement in the newborn

A

10 ug/kg

123
Q

Effect of gonadal steroids on the TBG and TSH

A

Estrogen - inc TBC- inc TSH

Androgen- dec TBG

124
Q

What are the other hormones that can affect thyroid function

A
  1. Glucocorticoids
  2. Gonadal steroids
  3. Growth hormone
125
Q

Normal TSH

A

0.4 to 4.2 mU/L

126
Q

Normal range

FREE T4

A

9- 30 pmol/L

0.7 to 2.5 ng/dL

127
Q

Normal range Free T3

A

3-8 pmol/L

0.2 to 0.5 ng/dL

128
Q

Thyroid hormone profile of sick euthyroid syndrome :

A

Is like central hypothyroidism
Dec FT3 then Dec Ft4
and TSH from Normal, decreases

On recovery phase, TSH increases first so the profile is like primary hypothyroidism

129
Q

TBG jn pregnancy / neonatal state / OCPd estrogen tamoxifen

A

Increased binding of TBG

130
Q

Biochemical markers increased in thyrotoxicosis

A

“VOUFASA” table

VWF
Osteocalcim
Urine pyridium collagen cross links
ferritin
ALP 
SHBG
ANP atrial natriuretic peptide
131
Q

Biochemical markers decreased in thyrotoxicosis

A

LDL

Lipoprotein a

132
Q

Biochemical markers decreased in hypothyroidism

A

Vasopressin

133
Q

This thyroid autoantibody is not found in the general population

A

TSHR -Ab
Found in 95 percent of graves disease

Tg-Ab 20% normal
Anti TPO 27% normal pop

134
Q

Half life of iodine 131

A

8.1 days

135
Q

Half life of iodine 123

A

0.55 day

136
Q

Define iodine deficiency

A

Urinary iodine excretion less than 100 ug/day

137
Q

States associated with increased RAIU aside from hyperthyroidism

A
  • aberrant hormone synthesis
  • iodine deficiency
  • response to thyroid hormone depletion (rebound after antithyroid therapy)
  • excessive hormone loss (nephrotic syn, chronic diarrhea, ingestion of soybean, cholestyramine)
138
Q

Prevalence of hyperthyroidism

A

1-2% in women

139
Q

Reason for the retraction of the upper and lower eyelids in hyperthyroidism

A

Increased adrenergic tone

140
Q

Clotting factor increased in thyrotoxicosis

A

Factor VIII

But note that the clotting mechanism is normal

141
Q

Effect of thyrotoxicosis on warfarin

A

Enhanced sensitivity to warfarin because there is accelerated clearance if vitamin K dependent clotting factora

142
Q

Drug induced thyroiditis

A

Sunitinib

Sorafenib

143
Q

Treatment of subacute thyroiditis

A

Glucocorticoids (pred 40 mg/day)
Aspirin / NSAIDs
if tsh is not suppressed you may add Levothyroxine

144
Q

Thyroid hormone profile of thyrotoxicosis factitia

A

Dec TSH
INC FT4 and FT3
Increased Tg
Normal RAIU

145
Q

Complications of RAI

A
  • thyroid cancer
  • mortality
  • hypothy (80 in 6 mos)
  • radiatjon thyroiditis (exacerbation of thyrotoxicosis 10-14 days after RAI)
146
Q

When should anti thyroid agent be withdrawn prior to RAI

A

3-7 days

147
Q

Goal of hyperthyroidism treatment during pregnancy

A

Maternal free T4 level just above the Upper normal nonpregnant range

NO ATTEMPT TO NORMALIZE TSH

thyroid drugs may overtreat fetus compared to the mother

148
Q

Period of risk of embryopathy of thyroid drugs

A

6-10 weeks pregnancy

149
Q

Hallmark of the immune effects initiated by the placenta

A

Fall in thyroid autoantibody secretion

150
Q

When does FT4 rise in pregnancy

A

Near the end of first trimester and is accompanied by partial TSH suppression

ENDOCRINE (12 decks)

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