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Endocrinology > Thyroid > Flashcards

Thyroid Flashcards

1
Q

Radio iodine uptake

Enlarged gland with increased tracer uptake that is distributed homogenously

A

GRAVES DISEASE

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2
Q

Radio iodine uptake

Focal areas of increased uptake with suppressed tracer uptake in the remainder of the gland

A

TOXIC ADENOMAS

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3
Q

Radio iodine uptake

Gland is enlarged with distorted architecture with multiple areas of relatively increased or decreased tracer uptake

A

TOXIC MNG

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4
Q

Radio iodine uptake

Very low Radio iodine uptake due to follicular cell damage and TSH suppression

A

SUBACUTE, VIRAL AND POSTPARTUM THYROIDITIS

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5
Q

Radio iodine uptake

Thyrotoxicosis factitia

A

Associated with low uptake

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6
Q

Thyroid scintigraphy
Functioning or hot nodules
Are they benign or malignant?

A

Almost never malignant

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7
Q

Recommended average daily intake of iodine

Adults

A

150-250 ug/day

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8
Q

Recommended average daily intake of iodine

Children

A

90-120 ug/day

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9
Q

Recommended average daily intake of iodine

Pregnant and lactating women

A

250 ug/day

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10
Q

This protein binds 80% of the thyroid hormones

A

Thyroid hormone binding globulin

Albumin bunds
10% T4 and
30% T3

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11
Q

Deficiency of this mineral may contribute to neurologic manifestations of cretinism

A

Selenium

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12
Q

These drugs suppress TSH

A

Dopamine
Glucocorticoids
Somatostatin

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13
Q

Time for TSH secretion after TRH secretion

A

15 mins

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14
Q

This is characterized by:

  1. Defective organification of iodine
  2. Goiter
  3. Sensorineural deafness
A

Pendred syndrome

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15
Q

There is marked lymphocytic infiltration of the thyroid with germinal center formation

  • atrophy of the thyroid follicles
  • oxtail metaplasia
  • absence of the colloid
  • mild to moderate fibrosis
A

Hashimoto’s thyroiditis

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16
Q

Extensive fibrosis, lymphocytic infiltration less pronounced, thyroid follicles completely absent

This represents the end stage of Hashimotos thyroiditis

A

Atrophic thyroiditis

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17
Q

Account for 50% of

Genetic disease associated with autoimmune hypothyroidism

A
  1. HLA DR polymorphisms
    HLA DR3, DR4, DR5
    2.!CTLA4, a T cell regulatory gene
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18
Q

Composition of thyroid lymphoid infiltrate in autoimmune hypothyroidism

Which PRIMARILY MEDIATES thyroid cell destruction

A

Activated CD4 and CD8 T cells
B cells

CD8 T cells mediate thyroid cell destruction by

1) performing induced cell necrosis
2) granzyme B induced apoptosis

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19
Q

Mechanism of myxedema in hypothyroidism

A

Increased dermal glucosamine glycol content traps water giving rise to skin thickening without pitching

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20
Q

Steroid responsive syndrome associated with TpO antibodies
Myoclonus
Slow wave activity on EEG

A

Hashimotos encephalopathy

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21
Q

Signs and symptoms of other autoimmune disease

Which may be found in autoimmune hypothyroidism

A 
Celiac disease
Dermatitis herpetiformis
Chronic active hepatitis
Rheumatoid arthritis
Systemic lupus erythematosus
Myasthenia Garcia
Sjögren's syndrome
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22
Q

% of patients with autoimmune hypothyroidism where thyroid associated ophthalmopathy is found

A

5%

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23
Q

Goal of treatment in secondary hypothyroidism

A

Maintain T4 levels in the upper half of the reference range

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24
Q

Replacement dose of levothyroxine if there is no residual thyroid function

A

1.6 ug/kg body weight
(100-159 ug)
Taken 30 mins before breakfast

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25
TSH monitoring once full replacement is achieved
2-3 yrs
26
Patient missed a dose levothyroxin e Skip dose Or double dose?
Double dose. T4 has a long half life
27
When to treat sub clinical hypothyroidism
TSH levels above 10 mIU/L Symptoms of hypothyroidism Positive TPO antibodies (+) evidence of heart disease
28
Treatment si clinical hypothyroidism and goal
Low dose L thyroxine 25-50 | Goal: normalize TSH
29
Idiosyncratic side effect of levothyroxine replacement in children
Pseudo tumor cerebri
30
TSH goals in pregnant women
31
Mortality rate of myxedema coma
20-40%
32
Clinical manifestations of myxedema coma
Reduced level of consciousness Seizures Hypothermia ``` Precipitated by: Drugs Pneumonia CHF MI GI bleeding CV events ```
33
Plays a major role in the pathoenesis of myxedema coma
HYPOVENTILATION, | Leading to hypoxia and hypercapnia
34
State of thyroid hormone excess
Thyrotoxicosis
35
Result of excessive thyroid function
Hyperthyroidism
36
Accounts for 60-80% of thyrotoxicosis
Graves' disease
37
Almost always arises in the background of Hashimoto's thyroiditis
Lymphoma
38
Features of thyrotoxicosis may be masked or subtle in the elderly, patients may present mainly with fatigue and weight loss, a condition known as
APATHETIC THYROTOXICOSIS
39
MC cardiovascular manifestation of thyrotoxicosis
Sinus tachycardia
40
Where is thrill or bruit thyroid best detected
Inferolateral margins of the thyroid lobes
41
Cause of lid retraction in Graves
Sympathetic overactivity
42
Earliest manifestation of ophthalmopathy
Sensation of grittiness Eye discomfort Excess tearing
43
Measurement of proptosis
Exophthalmometer
44
The most serious ocular manifestation of graves
Compression of the optic nerve at the apex of the orbit
45
Explaining the anatomical localization of immune response in ophthalmopathy
Orbital fibroblasts may be sensitive to cytokines
46
Most frequent location of thyroid dermopathy
Anterior and lateral aspects of the lower leg
47
Form of clubbing found in
Thyroid acropachy
48
Mechanism of action methomazole and ptu
Inhibition of the function of TPO, reducing oxidation and organification of iodide
49
FDA indications for the use of PTU over MMT
First trimester of pregnancy Thyroid storm Minor adverse reactions to methomazole
50
Dose of 131 iodine
370 mBq (10 mcI) to 555 mBq (15 mci )
51
Why ptu is the DoC in first trimester of pregnancy, and why shift to MMT later?
Aplasia cutis Choanal atresia Rare association with hepatotoxicity ?
52
Ratio when converting PTU to MMT in pregnancy
15-20 mg PTU to 1 mg MMT
53
PTU dose in thyroid crisis
Loading dose 500 to 1000 mg | And 250 every 4 h
54
Rationale iodide in thyroid storm | And why do you give it an hour after PTU dose
Block hormone synthesis via wolf chaikoff | Delay: to prevent excess iodine from being incorporated into the new hormone
55
Dose of Potassium iodide in thyroid storm
5 drops every 6 hrs
56
Due to suppurative infection of the thyroid
Acute thyroiditis
57
MC cause of acute thyroiditis in children and young adults
Presence of a pyriform sinus, a remnant of fourth branch mail pouch that connects the oropharynx with thyroid
58
Bacterial causes of thyroiditis
Staphylococcus Streptococcus Enterobacter
59
Subacute causes of thyroiditis
Viral or granulomatosis thyroiditis Silent thyroiditis , postpartum Mycobacterial infection Drug induced (IFN, amiodarone)
60
Also known as: Granulomatosis thyroiditis Viral thyroiditis De quervains thyroiditis
Subacute thyroiditis
61
Viruses implicated in subacute thyroiditis
``` Mumps Coxsackie Influenza Adenovirus Echovirus ```
62
Thyroid shows a characteristic patchy inflammatory infiltrate with disruption of the thyroid follicles and multinucleated giant cells with some follicles
Subacute thyroiditis
63
Subacute thyroiditis is a diagnosis often overlooked for this dx:
Pharyngitis
64
Complete resolution is usually the outcome in subacute thyroiditis, what is the % of subacute thyroiditis where permanent hypothyroidism is the outcome
15%
65
Three distinct phases over 6 months
1. Thyrotoxic phase 2. Hypothyroid phase 3. Recovery phase
66
Compare the T4/T3 ratio of subacute thyroiditis and Graves' disease or thyroid autonomy
Greater T4/T3 ratio in subacute than in graves due to disproportionate increase in T3
67
How to confirm subacute thyroiditis
High ESR | Low RAI
68
Rx symptoms of subacute thyroiditis
Large doses of aspirin 600 q4-6 If marked: Prednisone 40-60 mg!
69
Occurs in Px with underlying autoimmune thyroid disease and has a clinical course similar to that of acute thyroiditis
Painless thyroiditis/ silent thyroiditis
70
Painless/silent thyroiditis in 5% of women 3-6 mos after pregnancy (+) TPO antibodies ante partum
Post partum thyroiditis
71
Treatment differences subacute thyroiditis and painless thyroiditis
Glucocorticoids not indicated in painless thyroiditis Thyroxine replacement has a role in hypothyroid phase of painless thyroiditis
72
% of patients treated with IFNa who develop drug induced thyroiditis
5%
73
Rare disorder occuring in women | Insidious painless goiter with local symptoms due to compression
Riedels thyroiditis
74
MC cause of chronic thyroiditis
Hashimoto's
75
The most common hormone pattern in sick euthyroid syndrome
Decrease in total and unbound T3 levels (low T3) with normal T4 and TSH T4 conversion to T3 via perioheral deiodination is impaired ---> increased reverse t3)
76
Low T4 syndrome in sick euthyroid syndrome
Dramatic fall in t4 and t3 | Accelerated expression of type III deiodinase
77
Thyroid hormones | HIV infection
Inc t3 and t4 | T3 falls with progression to AIDS
78
Thyroid hormones | RENAL DISEASE
low T3 | Normal rt3 levels
79
Iodine content of amiodarone
39% by weight
80
MOA amiodarone induced thyrotoxicosis
Amiodarone inhibitors deiodinase activity | Metabolites function as weak agonists of thyroid hormone
81
2 types of AIT
Type 1 AIT + underlying thyroid abnormality Inc iodine (jod basedow) Type 2 No intrinsic thyroid abnormality Drug induced lysosomal activation
82
Factors that alter thyroid function in pregnancy
``` Inc HCG doc TSH Estrogen increase TBG Immune suppressed Placenta metabolizes thyroid hormone Inc urinary iodide excretion ```
83
Support Diagnosis of iodine deficiency
Low unemployment nary iodine levels
84
Approach to Px FNAB results Nondiagnostic
``` Repeat US guided FNA ⬇️ Nondiagnostic? ⬇️ Close ff up or surgery ``` 1-5% risk of malignancy
85
Approach to Px FNAB results Malignant
Pre op US or LN assessment ⬇️ Surgery 97-100% risk of malignancy
86
Approach to Px FNAB results Follicular neoplasm
Consider molecular testing Surgery if indicated with pre op US or LN assessment 20-30% risk of malignancy
87
Approach to Px FNAB results Atypia or follicular lesion of undetermined significance
Repeat US guided FNA or consider molecular testing
88
Risk of malignancy if read as "Benign"
2-4% risk
89
Follow up of si clinical hypothyroidism
6-12 wks
90
Origin of the word THYROID
``` THyreos= shield Eidos= form ```
91
Where is the thyroid gland located
Anterior to the trachea between the cricoid and Suprasternal notch
92
Development of the thyroid gland occurs when
3rd week of gestation
93
When does thyroid hormone synthesis begin?
11 weeks gestation
94
Give rise to the thyroid medullary C cells
Neural crest derivatives from the ultimobranchial body
95
Peak TSsH secretion occurs ___ min after administration of exogenous TRH
15 mins
96
Manner of TSH secretion
Pulsatile Highest levels at night Diurnal rhythm
97
Half life to TSH
50 min
98
This is located at the apical surface of the thyroid cells and mediates iodine effluent into the lumen
Pendrin
99
Defective organification of iodine, goiter and sensorineural deafness
Pendred syndrome
100
Level of urinary iodine in iodine sufficient populations
>10 ug/dL
101
Relative metabolic potency of T4 in comparison to T3
T4= 0.3 than of T3
102
When to treat subclinical hypothyroidism if TSH levels are below 10 mIU/L
1) symptoms of hypothyroidism 2) positive TPO antibodies 3) evidence of heart disease
103
Treatment of subclinical hypothyroidism
25-50 mcg levithyroxine with the goal of normalizing TSH
104
TSH goals during pregnancy in hypothyroidism
Increase L thyroxine by 50% in pregnancy Less than 2.5 mIU/ L during the 1st trimester 3 mIU/L 2nd and 3rd
105
Genetic cause of congenital hypothyroidism Resistance to TSH Autosomal dominant
Gsa | Albright hereditary osteodystrophy
106
Loss of iodide reutilization
Dehalogenase 1 defect
107
Affected in thyroid dysgenesis
PAX 8
108
Congenital hypothyroidism Affected, THYROID agenesis, choanal atresia, spiky hair
TTF- 2
109
Half life of TSH
50 mins
110
Graves' disease with antibthyroid drugs | Maximum remission rates are achieved by ____ months
12-18 mos
111
Elderly with CAD increase L thyroxine
Every 2-3 months
112
Elderly px versus younger patients dose of thyroxine
20% less

Endocrinology (8 decks)

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