endocrine 4 - thyroid Flashcards
(76 cards)
what do the thyroid follicles secrete
T3 and T4
what do the parafollicular cells secrete
calcitonin
what is the difference with the resting and the active follicle
active is enlarged and more plump, the central area is smaller but still filled with colloid
what amino acid and element are needed to make thyroid hormones
tyrosine and iodine
what are the intermediates to thyroid hormones
MIT and DIT
how is iodide taken into the cell
active transport by Na I pump
what is thyroglobulin
glycoprotein that contains tyrosine
what makes MIT
tyr + 1 iodine
what makes DIT
tyr + 2 iodine
what makes T3
MIT + DIT
what makes T4
DIT + DIT
how does TSH enhance thyroid hormone synthesis
increase Na I pump and increase thyroglobulin synthesis (first 2 steps)
what happens to T4 and T3 once they are made in the colloid
they are endocyzed from the lumen back into the cell
how are T3 and T4 released from thyroglobulin
lysosomal enzymes
what happens once T3 and T4 are released from thyroglobulin
they are secreted into the blood, I- and amino acids recycles
which thyroid hormone is secreted more into the blood
T4>T3
how is T3 and T4 transported in the blood
bound to thyroid binding protein
which T is more potent
T3
T4 is a prohormone
what happens to T4
it is converted into T3 in peripheral cells and liver
where does T3 bind
nuclear receptors (fat soluble)
what percent is T4 and T3 made
90% T4
10% T3
which thyroid hormone is a prohormone
T4
what stimulates TSH
TRH
where is TRH from
hypothalamus
