ENDOCRINE EXAM 3 WITH VERIFIED
ANSWERS
What rare rstimulating/inhibiting rfactors rfor rsecretion rof rTRH? r- rCORRECT✅✅-cold
r(stim)
-acute rpsychosis r(stim)
-circadian rand rpulsatile rrhythms r(stim)
-stress r(inhib)
TRH rstimulates rthe rrelease rof r___ rfrom rthe ranterior rpituitary. r- rCORRECT✅✅TSH
TSH rstimulates rthe rsynthesis rand rrelease rof r___ rand r___. r- rCORRECT✅✅T3
r(triiodothyronine), rT4 r(thyroxine)
T/F: rthe rthyroid rsystem rhas ra rnegative rfeedback rloop. r- rCORRECT✅✅True; rT3
rand rT4 rfeedback rto rinhibit rsynthesis rof rTRH rand rTSH
T/F: rHigh rlevels rof rIodine ris rrequired rfor rT4 rsynthesis. r- rCORRECT✅✅False, rlow
rlevels
How rdo rhigh rlevels rof riodine raffect rT4? r- rCORRECT✅✅High rlevels rinhibit rT4
rsynthesis rand rrelease rin ra rphenomenon rcalled rthe rWolff-Chaikoff rEffect rwhere
rorganification ris rinhibited rby rexcess riodine)
What ris rthe rpurpose rof rthyroid rfollicular rlumen? r- rCORRECT✅✅Site rof rstorage rfor
rthyroglobulin
What ris rthe rpurpose rof rthe rsodium-iodide rsymporter? r- rCORRECT✅✅Concentrates
riodide rin rthe rfollicular rcells
T3 rand rT4 rare rsynthesized rfrom? r- rCORRECT✅✅Tyrosine rand riodine r
-T3 rhas r3 riodine rand rT4 rhas r4 riodine
What ris rthyroglobulin? r- rCORRECT✅✅-A rlarge rglycoprotein rwhich rcontains
rprecursors rof rthe rthyroid rhormones r(tyrosine)
-It ris rproduced rby rthe rthyroid rfollicular rcells
-T3 rand rT4 rare rproduced rwhen rthyroglobulin's rtyrosine rresidues rare riodinated.
Iodide ris roxidized rby r___ rto riodine. r- rCORRECT✅✅Thyroidal rperoxidase r(TPO)
Describe riodide rorganification. r- rCORRECT✅✅TPO rrapidly riodinated rtyrosine
rresidues rwithin rthe rthyroglobulin rmolecule rto rform rmonoiodotyrosine r(MIT) rand rdiode
rtyrosine r(DIT)
,What ris rthe rratio rof rT4 rto rT3? r- rCORRECT✅✅5:1
Most rof rthe rhormone rreleased rfrom rthe rthyroid rgland ris rin rthe rform rof? r-
rCORRECT✅✅thyroxine r(T4)
What ris rthe renzyme rthat rconverts rT4 rto rT3 rin rthe rperipheral rtissues? r-
rCORRECT✅✅5' rdeiodinase
Describe rthe rsteps rin rthe rformation rof rT3 rand rT4. r- rCORRECT✅✅1. rI- renters rvia
rNa/iodide rsymporter rin rthe rbasement rmembrane ror rvia rpendrin rin rthe rapical
rmembrane r
2. rIodide ris roxidized rinto riodine rvia rTPO
3. rIodine rundergoes rorganification rby rattaching rand rbinding rto rtyrosine ron
rthyroglobulin rto rform rT3 rand rT4
4. rProteolysis ris rrequired rto rremove rthyroglobulin rfrom rT3 rand rT4 rso rthey rcan rbe
rreleased rinto rthe rblood
MIT r+ rDIT= r___, rDIT r+ rDIT= r___ r- rCORRECT✅✅T3, rT4
What roccurs rin rthe rinactive rphase rof rthyroid rhormone rMOA? r-
rCORRECT✅✅Corepressor rsuppresses rthyroid rreceptors
What roccurs rin rthe ractive rphase rof rthyroid rhormone rMOA? r- rCORRECT✅✅-
thyroid rhormones rbound rto rthyroid rbinding rproteins r(TBPs) rare rfreed rand rtransported
rinto rthe rcytoplasm
-T4 ris rtransformed rinto rT3 rby r5' rdeiodinase rand rmoved rinto rthe rnucleus
-heterodimers rwith rretinoid rX rreceptor r(RXR) rare rdisplaced ralong rwith rcorepressor
-coactivator rbinds rto rthe rthyroid rligand rbinding rdomain r(TR-LBD)
-TR-LBD rbinds rto rT3 rand ris rthen rconnected rto rthyroid rDNA rbinding rdomain r(TR-
DBD) rwhich rwill rincrease rexpression rof rproteins rat rthe rthyroid rresponse relement
r(TRE)
Which ris rmore rpotent rT3 ror rT4? r- rCORRECT✅✅T3
Which ris ra rprohormone rT3 ror rT4? r- rCORRECT✅✅T4
Why rdo rwe rmostly rgive rformulations rof rT4 ras rdrug roptions? r-
rCORRECT✅✅Because rit rhas ra rgreater rhalf rlife rand rcan rbe rconverted rin rthe
rperipheral rtissues rto rthe rmore rpotent rand rbiologically ractive rform, rT3
What rare rfunctions rof rthyroid rhormones? r- rCORRECT✅✅-responsible rfor roptimal
rgrowth, rdevelopment, rfunction rand rmaintenance rof rall rbody rtissues r
-critical rfor rdevelopment rand rfunction rof rnervous, rskeletal, rand rreproductive rtissues r
-secretion rand rdegradation rrates rof rall rother rhormones r(catecholamines, rcortisol,
restrogens, rand rtestosterone, rand rinsulin) rare raffected rby rthyroid rstatus
, What ris rcretinism? r- rCORRECT✅✅congenital rhypothyroidism rwhich rmay rresult rin
rirreversible rmental rretardation rand rdwarfism
T/F: rthyroid rhyperactivity rresembles rparasympathetic rnervous rsystem roveractivity. r-
rCORRECT✅✅False, rSYMPATHETIC
Why rdoes rthyroid rhyperactivity rmanifest ras rsympathetic rnervous rsystem ractivity? r-
rCORRECT✅✅-TH rincreases rthe rnumber rof rbeta rreceptors rand renhances
ramplification rof rbeta rreceptor rsignal r
-symptoms rinclude: rtremors, rexcessive rsweating, rtachycardia, ranxiety
How rdoes rhyperthyroidism raffect rthe rcardiovascular rsystem? r- rCORRECT✅✅-
decreased rperipheral rvascular rresistance
-increased rHR r(tachycardia*), rstroke rvolume, rcardiac routput, rand rpulse rpressure
-increased rinotropic rand rchronotropic reffects
-arrhythmias rand rangina
How rdoes rhyperthyroidism raffect rthe rGI rsystem? r- rCORRECT✅✅-increased
rappetite
-increased rfrequency rof rbowel rmovements
-hypoproteinemia
How rdoes rhyperthyroidism raffect rthe rCNS? r- rCORRECT✅✅-nervousness
-hyperkinesia
-emotional rlability
-agitation
How rdoes rhyperthyroidism raffect rthe rmetabolic rsystem? r- rCORRECT✅✅-increased
rBMR
-hyperglycemia
-increased rfree rfatty racids rand rfat rmetabolism
-increased rcarbohydrate rmetabolism r
-weight rloss
-decreased rcholesterol rand rTG
-increased rhormone rdegradation rand rdrug rmetabolism
-increased rrequirements rfor rfat rand rwater rsoluble rvitamins
-decreased rwarfarin rrequirement
What rare rcauses rof rchildhood rhypothyroidism r(cretinism)? r- rCORRECT✅✅-iodine
rdeficiency
-thyroid rdysgenesis
-inborn rerrors rof rhormone rsynthesis r
-**decreased rTPO
ANSWERS
What rare rstimulating/inhibiting rfactors rfor rsecretion rof rTRH? r- rCORRECT✅✅-cold
r(stim)
-acute rpsychosis r(stim)
-circadian rand rpulsatile rrhythms r(stim)
-stress r(inhib)
TRH rstimulates rthe rrelease rof r___ rfrom rthe ranterior rpituitary. r- rCORRECT✅✅TSH
TSH rstimulates rthe rsynthesis rand rrelease rof r___ rand r___. r- rCORRECT✅✅T3
r(triiodothyronine), rT4 r(thyroxine)
T/F: rthe rthyroid rsystem rhas ra rnegative rfeedback rloop. r- rCORRECT✅✅True; rT3
rand rT4 rfeedback rto rinhibit rsynthesis rof rTRH rand rTSH
T/F: rHigh rlevels rof rIodine ris rrequired rfor rT4 rsynthesis. r- rCORRECT✅✅False, rlow
rlevels
How rdo rhigh rlevels rof riodine raffect rT4? r- rCORRECT✅✅High rlevels rinhibit rT4
rsynthesis rand rrelease rin ra rphenomenon rcalled rthe rWolff-Chaikoff rEffect rwhere
rorganification ris rinhibited rby rexcess riodine)
What ris rthe rpurpose rof rthyroid rfollicular rlumen? r- rCORRECT✅✅Site rof rstorage rfor
rthyroglobulin
What ris rthe rpurpose rof rthe rsodium-iodide rsymporter? r- rCORRECT✅✅Concentrates
riodide rin rthe rfollicular rcells
T3 rand rT4 rare rsynthesized rfrom? r- rCORRECT✅✅Tyrosine rand riodine r
-T3 rhas r3 riodine rand rT4 rhas r4 riodine
What ris rthyroglobulin? r- rCORRECT✅✅-A rlarge rglycoprotein rwhich rcontains
rprecursors rof rthe rthyroid rhormones r(tyrosine)
-It ris rproduced rby rthe rthyroid rfollicular rcells
-T3 rand rT4 rare rproduced rwhen rthyroglobulin's rtyrosine rresidues rare riodinated.
Iodide ris roxidized rby r___ rto riodine. r- rCORRECT✅✅Thyroidal rperoxidase r(TPO)
Describe riodide rorganification. r- rCORRECT✅✅TPO rrapidly riodinated rtyrosine
rresidues rwithin rthe rthyroglobulin rmolecule rto rform rmonoiodotyrosine r(MIT) rand rdiode
rtyrosine r(DIT)
,What ris rthe rratio rof rT4 rto rT3? r- rCORRECT✅✅5:1
Most rof rthe rhormone rreleased rfrom rthe rthyroid rgland ris rin rthe rform rof? r-
rCORRECT✅✅thyroxine r(T4)
What ris rthe renzyme rthat rconverts rT4 rto rT3 rin rthe rperipheral rtissues? r-
rCORRECT✅✅5' rdeiodinase
Describe rthe rsteps rin rthe rformation rof rT3 rand rT4. r- rCORRECT✅✅1. rI- renters rvia
rNa/iodide rsymporter rin rthe rbasement rmembrane ror rvia rpendrin rin rthe rapical
rmembrane r
2. rIodide ris roxidized rinto riodine rvia rTPO
3. rIodine rundergoes rorganification rby rattaching rand rbinding rto rtyrosine ron
rthyroglobulin rto rform rT3 rand rT4
4. rProteolysis ris rrequired rto rremove rthyroglobulin rfrom rT3 rand rT4 rso rthey rcan rbe
rreleased rinto rthe rblood
MIT r+ rDIT= r___, rDIT r+ rDIT= r___ r- rCORRECT✅✅T3, rT4
What roccurs rin rthe rinactive rphase rof rthyroid rhormone rMOA? r-
rCORRECT✅✅Corepressor rsuppresses rthyroid rreceptors
What roccurs rin rthe ractive rphase rof rthyroid rhormone rMOA? r- rCORRECT✅✅-
thyroid rhormones rbound rto rthyroid rbinding rproteins r(TBPs) rare rfreed rand rtransported
rinto rthe rcytoplasm
-T4 ris rtransformed rinto rT3 rby r5' rdeiodinase rand rmoved rinto rthe rnucleus
-heterodimers rwith rretinoid rX rreceptor r(RXR) rare rdisplaced ralong rwith rcorepressor
-coactivator rbinds rto rthe rthyroid rligand rbinding rdomain r(TR-LBD)
-TR-LBD rbinds rto rT3 rand ris rthen rconnected rto rthyroid rDNA rbinding rdomain r(TR-
DBD) rwhich rwill rincrease rexpression rof rproteins rat rthe rthyroid rresponse relement
r(TRE)
Which ris rmore rpotent rT3 ror rT4? r- rCORRECT✅✅T3
Which ris ra rprohormone rT3 ror rT4? r- rCORRECT✅✅T4
Why rdo rwe rmostly rgive rformulations rof rT4 ras rdrug roptions? r-
rCORRECT✅✅Because rit rhas ra rgreater rhalf rlife rand rcan rbe rconverted rin rthe
rperipheral rtissues rto rthe rmore rpotent rand rbiologically ractive rform, rT3
What rare rfunctions rof rthyroid rhormones? r- rCORRECT✅✅-responsible rfor roptimal
rgrowth, rdevelopment, rfunction rand rmaintenance rof rall rbody rtissues r
-critical rfor rdevelopment rand rfunction rof rnervous, rskeletal, rand rreproductive rtissues r
-secretion rand rdegradation rrates rof rall rother rhormones r(catecholamines, rcortisol,
restrogens, rand rtestosterone, rand rinsulin) rare raffected rby rthyroid rstatus
, What ris rcretinism? r- rCORRECT✅✅congenital rhypothyroidism rwhich rmay rresult rin
rirreversible rmental rretardation rand rdwarfism
T/F: rthyroid rhyperactivity rresembles rparasympathetic rnervous rsystem roveractivity. r-
rCORRECT✅✅False, rSYMPATHETIC
Why rdoes rthyroid rhyperactivity rmanifest ras rsympathetic rnervous rsystem ractivity? r-
rCORRECT✅✅-TH rincreases rthe rnumber rof rbeta rreceptors rand renhances
ramplification rof rbeta rreceptor rsignal r
-symptoms rinclude: rtremors, rexcessive rsweating, rtachycardia, ranxiety
How rdoes rhyperthyroidism raffect rthe rcardiovascular rsystem? r- rCORRECT✅✅-
decreased rperipheral rvascular rresistance
-increased rHR r(tachycardia*), rstroke rvolume, rcardiac routput, rand rpulse rpressure
-increased rinotropic rand rchronotropic reffects
-arrhythmias rand rangina
How rdoes rhyperthyroidism raffect rthe rGI rsystem? r- rCORRECT✅✅-increased
rappetite
-increased rfrequency rof rbowel rmovements
-hypoproteinemia
How rdoes rhyperthyroidism raffect rthe rCNS? r- rCORRECT✅✅-nervousness
-hyperkinesia
-emotional rlability
-agitation
How rdoes rhyperthyroidism raffect rthe rmetabolic rsystem? r- rCORRECT✅✅-increased
rBMR
-hyperglycemia
-increased rfree rfatty racids rand rfat rmetabolism
-increased rcarbohydrate rmetabolism r
-weight rloss
-decreased rcholesterol rand rTG
-increased rhormone rdegradation rand rdrug rmetabolism
-increased rrequirements rfor rfat rand rwater rsoluble rvitamins
-decreased rwarfarin rrequirement
What rare rcauses rof rchildhood rhypothyroidism r(cretinism)? r- rCORRECT✅✅-iodine
rdeficiency
-thyroid rdysgenesis
-inborn rerrors rof rhormone rsynthesis r
-**decreased rTPO
