B8-058 Hypothyroidism Flashcards
in primary hypothyroidism, TH will be […] and TSH will be […]
in hypothyroidism, TH will be [low] and TSH will be [high]
anti-TPO or anti-thyroid globulin antibodies would indicate
Hashimotos
why do you give T4 over T3?
longer half life
treatment for hypothyroidsm
levothyroxine
how does hypothyroidism increase prolactin?
low T3/4 —> increased TRH/TSH –> increased prolactin
[…] play a role in regulating TBG levels
estrogens
(low estrogen –> low TBG –> low SHBG)
prolactin inhibits […] causing amenorrhea
GnRH
how does hypothyroidism impact the menstrual cycle leading to amenorrhea?
low T3/T3 stimulates TRH release
TRH stimulates prolactin release
Prolactin stimulates CRH release
CRH inhibits GnRH release
–> decreased FSH —> decreased estrogen
how does hypothyroidism cause galactorrhea?
low T4 and T3 lead to increased TRH and prolactin
increased prolactin causes excess milk production
normal T4 despite low TSH
(outside of pregnancy)
subclinical hypothyroidism
(antibodies “masking” TSH receptors)
in the first trimester, […] can bind TSHR to stimulate the thyroid gland
hCG
(may need to stop levothyroxine if taking)
what maintains elevated thyroid hormone levels in the 2nd and 3rd trimesters?
high levels of TBG (from high estrogen) slows degradation of hormones
thyroid receptor antibodies can be both […] and […]
inhibitory
stimulatory
(subtypes coexist but dominant subtype will determine physiologic response)
normal T4 despite low TSH in pregnancy could be caused by
mother with hypothyroidism, but hCG and TBG are compensating
high levels of estrogen secreted by the placenta in pregnancy stimulate hepatic production of
TBG, SHBG
increased TBG will lead to an [increase/decrease] in circulating hormone levels
increase
high levels of […] can induce prolactin to downregulate GnRH secretion and ovarian function
TRH
secondary hyperthyroidism is caused by
excessive secretion of TSH from thyrotropes
primary hyperthyroidism is caused by
excessive secretion of thyroid hormone
TSH independent
TSH would be […] in primary hyperthyroidism
decreased
TSH would be […] in secondary hyperthyroidism
increased
eyelid lag/retraction
periorbital puffiness
exophthalmos
are characteristic of
Grave’s
Grave’s disease is […]thyroidism
hyper
Hashimotos’s disease is […]thyroidism
hypo
describe expected TBG, total T4 and free T3 levels in a normal pregnancy
increased TBG
increased total T4
normal free T4
increased hCG causes a decrease in […] during the first trimester
TSH
hCG can bind TSH receptors and stimulate TH production
free T3/T4 levels [increase/decrease] in the second and third trimesters
decrease
i think decrease back to normal as hCG lowers and estrogen stabilizes?
increased TBG during the first trimester causes [increased/decreased] total T3/4
increased
Free T3/4 remains the same or just slightly elevated
estrogen stimulation of the liver increases the production of […] in pregnancy [3]
TBG
SHBG
albumin
primary hypothyroidism is caused by
insufficient thyroid hormone production
(TSH will be high)
secondary hypothyroidism is caused by
pituitary disorders (adenoma)
TSH will be low
TSH will be […] in primary hypothyroidism
high
TSH will be […] in secondary hypothyroidism
low
