5 - Thyroid gland Flashcards
hormone of thyoid galnd
t3 and t4
t3
triiodothyronine
t4
thyroxine
what are c clels
they secre calcitonin - the ca regulating hormone
what are follicular cells
they support the thryoid syntheis and surround the hollow cells, produng enzymes that make thyroid hores and thyroglobulin
concentrate iodide from the plasma and transport it to the colloid
what is in teh centre of the thyroid follicles
colloid - whihc has 2 - 3 months supply of th
thyroglobulin
a large protin rich in tyrosine resiules
what are tyrod hormes made from
tyrosine resius and iodide
how does iodien enter the follicular celsl
though the na+/I- tranpoerter symport, this takes up iodien against a conception gradient
how does iodien move form teh follicular cells to the colloid
thrugh the pendrin transpeorter
what happens in the thyroid due to tsh
parts of the colloid are taken to the follicular cell, where they are packaged into vesicules with proteolytic enzymes which cut the thryoglobuin and release thyroid hormoens
why do t3 and t4 need to be stored in vesicules
as they are lipid soluble so would be pass out of the foliuclar cell membrane
what to t3 and t4 bind to whwhen they leave the thyroid
thyroxine bind globulin
what is mit
onoiodotyrosine - addition of one iodine to tyrosine
what is dit
diiodotyrosine - adding a second iodine to mit
what is mit conguating with dit
t3
what is dit congulating with dit
t4
what turns iodide to iodine
enzyes exocytosed in the colloid
what percent of t3 and t4 are not plasma bound
0.2%
half life of t4 and t3
t4 - 6 day
t3 - 1 day
why is half life of t4 higher then t 3
as thyroxine bind globulin has a higher affinity for it prealiin git slowly into the plasma
what triggers tsh and trh, free hormones or hormone bound to thyroxine
only free hormones
is there more t4 or t3
about 50 times more t4 than t3
whihc binds to the cell more frequenly t3 or t4
t3
