Thyroid Flashcards
thyroid hormone is stored in
TGB follicular cells
TGB follicular cell secrete what?
calcitonin
T4 is completely active or inactive?
inactive, it’s a prohormone
T3 is biologically active or inactive?
active
T4 and T3 are all derived from what?
tyrosine, like the catecholamines
where is tyrosine taken up from?
the blood
after tyrosine is taken up from the blood what two reactions occur??
iodination and conjugation
how is thryoglobuline (TGB) formed? by synthesis of what
peptide chains in the ER + glycosylation in the golgi
iodination and conjugation occur within what?
TGB at apical border of the cell
Thyroid hormones are stored
within the TGB in colloid for up to 2 montsh
mechanism of secretion
endocytosis of colloid into follicular cells
how much T4 is secreted?
90ug a day
how much T3 is secreted?
4 ug a day
fate of T4 secreted is 35% converted into
T3
fate of T4 secreted is 45% converted to
reverse T3
fate of T4 secreted is 20% is
destroyed
what is T4’s 1/2 life?
long ~6 days
what is T3’s 1/2 life?
pretty long ~1-3 days
what kind of receptor does T3 have?
nuclear receptor
binds to nucleus and alters transcription
T3 is basically what kind of hormone?
a maintenance hormone
what is T3 required for??
growth process!!
if deficient in T3 you get
dwarfism
if you have excess T3 you get
stunted growth
T3 deficiency in children in the nervous system causes what?
cretinism, mental retardation
when must T3 be present or else cretinism is permanent?
during the 1st 3 months of life
T3 deficiency in adults causes
listless, sleepy, weak
T3 excess in the nervous system causes
hyper excitability
in terms of protein metabolism, excess T3 causes
increased gluconeogenesis, protein loss
in terms of protein metabolism, deficiency in T3 causes
myxedema, accumulation of mucopoly, a saccharide in skin
T3 is needed for normal function in many things… like:
lactation digestion kidney function cardiovascular function reproduction heat production
graves ideas is what type of thyroid state?
hyperthyroid state
associated with protrusion of eyes
hypothyroidism symptoms include:
sluggishness mental retardation reduced growth rate thick/dry skin sensitive to cold increased sleep
causes of hypothyroidism include:
poor development of thyroid
thyroid insensitive to TSH
or hashimoto’s disease
