SRGRY - THYROID Flashcards
6 steps of thyroid hormone synthesis
TOICHD
Trapping - NIS Organification - TPO Iodination - TPO Coupling - TPO Hydrolysis Deiodination - Dehalogenase
epithelial lining of thyroid
simple cuboidal epithelium
average daily iodine rqt
0.1mg
percentage of iodine stored in thyroid
> 90%
active form of thyroid hormone
T3
percentage of unbound thyroid hormone
0.02%
result of deiodination of inner ring of T4, a metabolically inactive compound
rT3
half life of T3
half life of T4
1 day
7 days
hormone from hypothalamus that stimulates pituitary to release TSH
TRH
excessively large doses of iodide lead to initial increased organification followed by suppression
Wolf Chaikoff effect
stimulate/depress thyroid function
hCG
Epinephrine
Glucocorticoid
stimulate
stimulate
inhibit
peripheral thyroid hormones may be reduced without compensatory increase in TSH levels, giving rise to
euthyroid sick syndrome
mechanism of increase in oxygen consumption basal metabolic rate and heat production by thyroid hormone
Na-K-ATPase stimulation
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
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
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
normal level of TSH
0.5-5 microU/mL
conditions with increased Tg and Total T4 making them not suitable screenung tests
increased estrogen
increased progesterone
congenital ds
conditions withe decreased Tg qnd TT4
anabolic steroid use
protein losing disorders like nephrotic syndrome
total t4 reference range
55-150nmol/L
T3 reference range
1.5-3.5nmol/L
end-organ resistance ro T4
Refetoff’s syndrome
free T4 reference range
12-28pmol/L
free T3 reference range
3-9pmol/L
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
5%
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
D
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
C
% Hashimoto’s with with hyperthyroidism
5%
% 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
D
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
