Thyroid h Flashcards by Daphne Galang

Thyroid

Micro L
Cystic 
Peripheral vascularutt
Round shape
—-

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Type 1 deiodinase

Outer and inner Rung

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Deiodinase

Subcellular location in endoplasmic reticulim

Type 2

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Deiodinase

Outer ri g

Type 2

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Deiodinase

High susceptibility to PTU

Type 1

Inner and outer

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Deiodinase

Decreased response to increased T4 (the rest increases)

Type 2

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Deiodinase

Source of plasma t3 in thyroyoxic patients

Type 3

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Deiodinase

Found in liver kidney thyroid pituitary

Type 1

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Effects of thyrotoxicosis in CV system

> decreased peripheral vasc resistance to dissipate heat

> inc CO inc HR inc SV

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Mechanism of increased cardiac contractility in thyrotoxicosis

Increase in ratio of alpha to B myosin chain

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Mearns Lerman scratch

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

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% of px with unexplained atrial fibrillation who are thyrotoxic

15%

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Percent of px with thyroxtoxicosis who have atrial fibrillation

2-20%

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Most common thyroid neoplasm

Folliculae adenoma

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Dose of rTSh

0.01 to 0.03 mg

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TNM scoring

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

Oxyphilic / oncocytic/ hurthle cell adenoma

alignant

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PTC variant with poor progmostic finding

Hobnail variant with micropapillary pattern

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PTC variant cells twice as tall as they are wide

Tall cell variant

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PTC variant prominent nuclear stratification of elongated cells

Columnar cell variant

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Aggrassive variants

Tall cell

Columnar cell variant

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Nuclear changes in FNA

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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Protooncogene whose activation is found only in PTC

RET

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Where is RET found

Chr 10q11-2

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% of thyroid malignancies that are medullar

Mutation found in tall cell bariant of PtC

BRAF Associated with higher risk of recurrence

Age papillary thyroid CA

30- 50 yrs

Female predominance of ptca

FTC

Invasion of capsule blood vessel or adjacent thyroid

CA more common in areas with iosine deficiency

Folliculae CA

Oncogene in FTCs

RAS oncogene

Cytogenetic abnormality limited to FTC

P arm chromosome 3

Age anaplastic thyroid CA

After 60 yrs FTC- 50 yrs ave

Hypothyroidism without a goiter

Atrophoc thyroiditis

Commoneat cause of goiter in iodine sufficient regions

Hasimotos

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

Hasimoto

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

THYROID LYMPHOMA

Impairment of intrathyroidL Nd peripheral deiodinatjon of iodotyrosines

Ipdotyrosine dehydrofenSe defect | DEHAL1B gene

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

Consumptive hypothyroidism

Contained in cassava

Linamarin

Tsh goal of treafment in Hashimoto

Tsh in the lower half of the reference interval

Action of lithium and why it causes hypothyroidism

Inhibirs thyroid hormone release | In high concentrations can inhibit organic binding reactions

Pendred syndrome

Defect in iodine organificatkon and sensory nerve deafness

Difference in finding: | Painful versus painless subacute thyroiditis

Painful- small and atrophic | Painless- enlarged and dfirm infiltraion

% of thyroid independent of pituitary | Why central is leas severe than primary hypothyroidism

10-15%

Expressed by visceral hemangiomas

Defects in this gene causes hereditary hypothyroidism

POUf1 Nd prop 1

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

Mutation in thyroid hormone receptor B | Interferes capacity of receptor to respond normally to T3

Presentation of patients witb RTH

Mix of hyper and hypo Palpitations and tachy Growth retardation

Profile of RTH patient

inc ft4 N or alightly increased tsh Tachy Goiter

Treatment of RTH

TRIAC

Time required for conplete equilibriation of FT4

6 weeks

% of levothyroxine absorbed in stomach

80%

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

22-34% higher

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

20-30% less

Increase thyroid hormone requirement in elederly

First trimester

Reasons dor the increase req of thyroid hormone in the fieat trimester of pregnancy

- increased T4 binding - increased colume of distribution of T4 - increase in D3 in placemta

Dose levothyroxine myxedema coma

Levothyroxine 500-800 IV Then 100 IV thereafter Hypertonic Saline!!! IV liothyrosine 25 ug q12

Rx reidel thyroiditis

Tamoxifen

Acute thyroiditis VS Subacute thyroiditis Preceding upper respiratory infection Fever Soretbroat

Acute

Acute thyroiditis VS Subacute thyroiditis | Paiful thyroid swelling

100- acute | 77- subacute

Acute thyroiditis VS Subacute thyroiditis | Left side affectes

Acute

Acute thyroiditis VS Subacute thyroiditis | Migratory thyroid tenderness

Sibacute

Acute thyroiditis VS Subacute thyroiditis Abnormal thyroid hormone levels Elevated or depressed

Subacute

Acute thyroiditis VS Subacute thyroiditis FNAB Purule t bacteria fungi

Acute In subacute - lymphocytes macriphage giant cells

Acute thyroiditis VS Subacute thyroiditis | Response to GC treatment

Acute transient | Subacute 100%

Acute thyroiditis VS Subacute thyroiditis | Gallium scan positive

Both

Thyroid fibrosis in middle aged women

Riedel chronic sclerosing thyroiditis

Tissue location of type 1 deiodinase

Liver Kidney Thyroud Pituitary Type 2 Cns brown adipose tissue heart skeletal muscle placenta Tupe 3 placenta cns hemangiomas

Half life of T 3

0.75 days

The most impt thyroid hormone inactivating emzyme

Recommended iodine dose pregnant

200 ug Adults 150 ug Childreb 90-120 ug

Naturally occuring I

I 127

Suggested starting dose of MMI in the setting of AIT Ata guidelines

40 mg OD

How are T3 and T4 transportes across cellular membranes

MCT8 | MCT10

Proteins facilitating transport of T4 and T3 across cell membranes

Mct8 and mct10

Transport of T4 across blood brain barrier

OAYP1C1

Mutation in the MCT8 gene Mental retardation Increased T3 Dysarthria Athetoid movements

Allan Herndon Dudley Syndrome

Rx for mct8 gene mutation

``` PTU with LT4 Diiosithyropropionic acid (DITPA) ```

Most impt pathywat for T4 metabolism

Outer ring D1 and D2 And is 80% of the source of T3 for humans

Diff of D1 Nd d2

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

To convert T4 nmol to ug/dl

Divide by 12.87

Half lfe of TBG

5 days

% of T3 bound by TBG

T3 80% | T4 64 %

Blocka aynthesis of TBG

L asparahinase

Major thyroid hormone binding protein in the csf

Transthyretin (TTR) Found in choroid plexus

Moa if iopanoic and iopodipie acid

Inhibit deiodinases

Iodine per drop of sski

38 mg/drop Lugols 6 mg/drop

Quantity of iodine required to supress tadioactive iodine to <2

> 30 mg/day

Iodine content per iodized salt

760/10 g

Iodine content angiographic and CT dyes

400-4000 mg/dose

How growth hormone affects thyroud

Decrease D3 activity outer ring deoidination

Biochemical markers of thyroid status | Decreased during thyrotoxicosis

Low low LDL Lipoproteins

Biochemical markers of thyroid status | Increased during thyrotoxicosis

``` Vw Osteocalcin Urine pyridium Ferritin ALP Sex hormone BG ANP ```

Decreased during hypothyroidiam

Vassopressin

Spared graves ophthalmoplegia

Muscle tendons spared | With lateral rectua least commonly affected

10 mg carbimaxole is metabolized to ___

6 mg methimazole

Multinodular toxic goiter

12-14 mci

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

Viral thyroiditia Subacute De quercain Ganulomatous

Histopath subacute thyroiditis/ | Giant cell thyroiditis

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

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

Subacute thyroiditis De quercain Granulomayous Giant cell

Viral infection of thyroid gland preceesed by URt

Subacute thyroiditis

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

Lack of elecation if ESR in hasimotis

Rx compromised Cv function hypothyroid

DITPA

Acute thyroiditis commonly affeects

Left lobe

1 mCi= __ MBq