thyroid disorders Flashcards
what is the primary mechanism of hyperlipidemia in hypothyroidism ?
decrease in LDL receptor density
what is myxedema ?
also called thyroid dermopathy
non pitting edema in hypothyroidism
usually in the face and around the eyes
pretibial myxedema is v common in graves
what is a myxedema coma ?
coma associated with hypothyroidism
what finding is associated with hypothyroid myopathy ?
increase in creatine kinase
what is the cause of hyponatraemia in hypothyroidism ?
high levels of ADH ( causes SIADH)
what are the thyroid replacement drugs ?
levothyroxine
what is thyroid storm ?
life threatning hyperthyroidism ( thyrotoxicosis)
what is the trigger for the occurence of thyrotoxicosis ?
usually an acute stressful event
usually happens in a patient with a pre existing hyperthyroid disease
after surgery, traum or infection
what is the pathophysiology associated with thyrotoxicosis, and what is the usual cause of death ?
surge of catecholamines
tachycardia - with death from arrythmias
what is a goiter ?
enlarged thyroid
what is the best initial test for thyroid disease ?
TSH
what is central thyroid disease ?
moshkela fel pituitary gland
low tsh
what is pituitary resistance to thyroid hormone ?
high levels of T3 and T should suppress the production of TSH
in this case TSh stays high
T3 and T4 are also high
what is reverse T3 ?
an isomer of T3
what is the special use of reverse T3 ?
increased levels of it in euthyroid sick syndrome
when should you suspect euthyroid sick syndrome ?
patient that has gone through some form of stress - surgery, infection
weaned off a ventialtor
normal TSH levels
normal T4
elevated levels of rT3
what is the most common cause of hyperthyroidism ?
graves disease
what is the pathophysiology of graves disease ?
activating autoantibodies against the TSH receptors (TSI)
what is the clinical presentation associated with graves disease ?
exopthalmous
pretibial myexedma
hyperthyroid plus exopthalmous
what is the pathology that causes the specific presentation of exopthalmous and pretibial myexedema in graves disease ?
t cell lymphocyte activation of fibroblasts
these fibroblasts contain TSH receptors
their stimulation leads to the secretion of glycosaminoglycans - draws in water
what is the treatment of graves disease ?
beta blockers , thionamides
thionamides : PTU or methimazole
what are the different mechanisms for the thionamides ?
methimazole : inhibits TPO
PTU : inhibits both TPO and 5 deiodenase
what are the side effects associated with thionamides ?
rash
agranulocytosis
hepatotoxicity
methimazole is teratogenic
which of the drugs is safe for pregnant women who are hyperthyroid ?
PTU
what is the treatment for thyroid storm ?
propanolol
thionamides
SSKI - to shut off T4 production
steroids
why are steroids given in thyroid storm ?
to treat any possible side effects of adrenal insufficiency
how is graves ophthalmology treated ?
with steroids
what are toxic adenomas and what is the pattern of iodine uptake ?
1- nodules in the thyroid that function independently
2- usually contain mutated TSH receptor
3- they do not respond to TSh
hot uptake on one side on radioactive iodine
what are the findings associated with toxic adenoma ?
el heya toxic multi nodular goiter bardo
palpable nodule
hyperthyroidism symptoms
what is the treatment for toxic adenoma ?
radioactive iodine or surgery
what are the contraindication of using radioactive iodine ?
breast feeding
pregnancy
what are the different rsults associoated with radioactive iodine?
hot nodule - non cancerous
cold nodule - often more suspicious , need to be biopsied
what is the jod basedow phenomenon ?
iodine induced hyperthyroidism
often occurs in areas with iodine deficiency
also usually happens in patients who already have toxic adenoma
what are the triggers associated with the occurence of jod-basedow phenomenon ?
drugs administered with high iodine content
expectorant ( potassium iodide )
Ct contrast with dye
amiodarone
what are the types of hyperthyroidism associated with amiodarone ?
type 1 - pre existing thyroid disease
type 2 - destructive thyroiditis , excessive release of T3 and T4 , can occur in patients without pre existing thyroid disease
most common cause of hypothyroidism ?
hashimotos thyroiditis
how can excess iodine cause hypothyroidism ?
by the wolff chaikoff effect
how does an iodine load cause hyperthyroidism ?
through thr jad- basdow effect
in a patient with a pre existing thyroid condition who then takes an iodine load
what are the goitrogens ?
iodine
lithium
cassava
millet
how does amiodarone cause hypothyroidism ?
1- excess iodine - through the wolff chaikoff effect
byroo7 lwa7do
some patients who have pre existing thyroid disease have “ failure to escape”
2- mimics T4
what are the mechanisms in which amiodarone causes hypothyroidism ?
iodine load
thyroiditis
what must be done before starting amiodarone ?
check TSH levels
what syndrome happens with congenital hypothyroidism ?
cretinism
what is the most common cause of cretinism?
dysfunctional TPO
what are the physical features associated with cretinism ?
mental retardation
coarse facial features
short stature
umbilical hernia
enlarged tongue
what are the causes of iatrogenic hypothyroidism ?
thyroid surgery
radioiodine therapy
neck radiation
what is the cause of hashimotos thyroiditis ?
ly,phocytes infiltrate the thyroid gland
autoimmune
what is the histology associated with hashimotos ?
massive lymphocytic infiltrate (germinal centres)
hurthle cells (enlarged eosinophilic follicular cells)
what risk is carried with hashimotos ?
increased risk of non hodgkin b cell lymphoma
what is the other name for subacute thyroiditis and what is the associated pathology ?
also called de queverian thyroiditis
granulomatous inflammation of the thyroid
what is riedel’s thyroiditis ?
fibroblast activation and proliferation
rock hard thyroid
extends byond the thyroid
what are the extra-thyroid manifestations of riedels disease ?
parathyroid gland affection - hypoparathyroidism
recurrent laryngeal nerve damage - hoarsness
trachea compression - difficulty breathing
what is the immunology associated with riedel’s thyroiditis ?
IgG4 plasma cells
what is lymphocitic thyroiditis ?
painless thyroiditis
a variant of hashimotos
can look like graves but with no clinical findings
what are the causes of drug induced thyroidits and what is the iodine uptake pattern ?
caused by lithium or amiodarone
will present with decreased iodine uptake on RAIU
what are the features of subclinical hypothyroidism ?
increased TSH
normal T3 and T4
what can riedel thyroiditis sometimes mimic ?
anaplastic thyroid carcinoma
what is struma ovarii ?
ovarian tumor secreting T3 and T4
