SRGRY - THYROID Flashcards by 18 22

6 steps of thyroid hormone synthesis

TOICHD

Trapping - NIS
Organification - TPO
Iodination - TPO
Coupling - TPO
Hydrolysis
Deiodination - Dehalogenase

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epithelial lining of thyroid

simple cuboidal epithelium

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average daily iodine rqt

0.1mg

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percentage of iodine stored in thyroid

> 90%

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active form of thyroid hormone

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percentage of unbound thyroid hormone

0.02%

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result of deiodination of inner ring of T4, a metabolically inactive compound

rT3

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half life of T3

half life of T4

1 day

7 days

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hormone from hypothalamus that stimulates pituitary to release TSH

TRH

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excessively large doses of iodide lead to initial increased organification followed by suppression

Wolf Chaikoff effect

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stimulate/depress thyroid function
hCG
Epinephrine
Glucocorticoid

stimulate
stimulate
inhibit

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peripheral thyroid hormones may be reduced without compensatory increase in TSH levels, giving rise to

euthyroid sick syndrome

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mechanism of increase in oxygen consumption basal metabolic rate and heat production by thyroid hormone

Na-K-ATPase stimulation

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effects of thyroid to heart and mechanism

positive inotropic and chronotropic effect via increase transcription of Ca ATPase and increase in B adrenergic receptors and concentration of G protein

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effects of thyroid hormone except

a. increase heart rate
b. increase GI motility
c. maintain hypoxic drive
d. maintain hypercaonic drive
e. increase speed of muscle contraction and relaxarion

AOTA

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T about thyroid function test

a. TSH is sufficient to assess thyroid function in all situations
b. T4 is the only test necessary in most patients with thyroid nodules that clinically appear euthyroid
c. Total T4 levels reflect the output from thyroid glabds
d. T3 levels in nonstimulated thyroid gland are more indicative of peripheral thyroid hormone metabolism

C and D

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normal level of TSH

0.5-5 microU/mL

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conditions with increased Tg and Total T4 making them not suitable screenung tests

increased estrogen
increased progesterone
congenital ds

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conditions withe decreased Tg qnd TT4

anabolic steroid use

protein losing disorders like nephrotic syndrome

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total t4 reference range

55-150nmol/L

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T3 reference range

1.5-3.5nmol/L

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end-organ resistance ro T4

Refetoff’s syndrome

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free T4 reference range

12-28pmol/L

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free T3 reference range

3-9pmol/L

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Ft4 test is confined to

cases of early hyperthyroidism in which total T4 is normal but FT4 is elevated

FT4 is most useful in

confirming diagnosis of early hyperthyroidism

how to evaluate TSH secretory function

500micrograms of TRH intravenously, measure TSH levels after 30-60 min

what percentage of Hashimoto's thyroiditis | have elevated thyroid antibody levels

80%

most important use of Tg

monitoring px with differentiated thyroid CA for recurrence

serum calcitonin nornal value

0-4 pg/mL

halflife of iodine 123

12-14 hours

halflife of Iodine 131

8-10 days

risk of malignancy for hot nodules

20%

risk of malignancy for cold nodules

thyroid utz most helpful

assessing cervical lymphadenopathy and gude biopsy

peak incidence of Grave's (age)

40-60 y.o.

diffusely and smoothly enlarged with a concomitant increase in vacularity

Grave's

what percentage of patients of Grave's have ophthalmopathy

50%

lid lag in Grave's

Von Graefe's

spasm of upper eyelid revealing sclera above corneoscleral limbus

Dalrymple's sign

etiology of Grave's ophthalmopathy

orbital fibroblasts and muscles have TSH-r result from inflammation caused by cytokines released from sensitized killer T lymphocytes and cytotoxic antibodies

findings in Grave's except a. exophthalmos b. gynecomastia c. onycholysis d. NOTA

confirmatory test for grave's

I-131 elevated uptake with diffusely enlarged gland

The following are diagnostic of Grave's a. elevated Anti-Tg b. elevated Anti- TPO c. elevated TSH-R d. elevated TSAb

C and D

Dosage of PTU

100-300mg 3x daily

dosage of methimazole

10-30mg 3x daily

MOA of methimazole and PTU

reduce thyrois hormone production by inhibiting the organic binding of iodine and the coupling of iodotyrosines (mediated by TPO)

additional MOA of PTU

inhibits peripheral conversion of T4 and T3

anti thyroid drug of choice

methimazole

anti thyroid DOC for pregnant

PTU | less placental transfer

Antithyroid drug associated with congenital aplasia

methimazole

anti thyroid DOC for breastfeeding

PTU

side effect of anti thyroid medication

``` grabulocytopenia skin rashes fever peripheral neuritis polyarteritis vasculitis hepatitis ``` rarely: agranulocytosis and aplastuc anemia

management of agranulocytosis resulting from anti thyroid med

admission to the hospital discontinuation of drug broad spectrum antibiotics

granulocyte level that must be achieved for surgery to proceed

1000cells/mm3

rekoase rate for Grave's with anti thyroid medications

40-80%

The following will most likely have recurrence EXCEPT a. nontoxic goiters 50g b. markedly elevated thyroid hormone levels c. nrgative or low titers of thyroid hormone receptor antibodies d. rapid decrease in gland size with anti thyroid medications

C and D

dose if oroprabolol for B blockade in symptomatic thyrotoxicosis

20-49mg 4x daily

symptomatic medication for tachycardia in thyrotoxicosis in asthmatic px

Calcium channel blocker

aside from control of tachycardia additional benefit does B blocker have?

decrease peripheral conversion of T4 to T3

in ox wih Grave's given RAI, px will become euthyroid after

2 mos

what percentage will becime hypothyroid after 1 yr RAI

2.5%

% of ox with progression if Grave's ophthalmopathy after RAI? after surgery?

33% 16%

thyroid gland is pale, gray-tan cut surface that is glandular, nodular, firm a. Grave's b. Riedl's thyroiditis c. Hashimoto's thyroiditis d. painless thyroiditis

% Hashimoto's with with hyperthyroidism

% Hashimoto's with hypothyroidism

20%

what confirms diagnosis of hashimoto's thyroiditis?

elevated TSH and presence of thyroid autoantibodies

Riedl's thyroiditis is a.k.a

invasive fibrous thyroiditis

mainstay trewtment for riedl's thyroiditis

surgery

thr goal of surgery in riedl's thyroiditis

decompress trachea | tissue diagnosis

riedl's thyroiditis medical mgt

corticosteroids tamoxifen mycophenolate mofetil - most dramatic

px with goiter and hoarseness, what do you suspect?

malignancy

FNAB is recommended in the ff except a. dominant thyroid nodule b. painful enalrging thyroid nodule c. both d. neither

true about mtc a. amyloid is a diagnostic finding b. calcitonin is a diagnostic tumor marker c. polygonal or spindle shaped cell d. stain positively for CEA

AOTA

percentage of MTC with familial ds

25%

tx of choice for MTC

thyroidectomy