thyroid hormones Flashcards
what are 2 main thryroid hormones
T3 and T4
what are substrates and enzymes to make T3 and T4
thyroglobulin > peroxidase
how to tell if thyroid is active
active- small follicles - cuboidal cells
inactive - large follicles - abundant colloid
what are steps to make T3/4
- transport I into colloid
- attach I to thyroglobulin
- phagocytose T3/4
- back into blood
what is iodine requirment
150ug/day
how does T3/4 circulate
protein bound (TBG, albumin, transthyretin)
what up-regs thyroid binding proteins
- estrogen and preg.
- methadone/heroin
- tranquiizers
what down regs. thyroid binding proteins
- glucocorticoids
- androgens
- anti-cancer drugs
which thyroid hormone is more active and which is more common
T3 more potent, but T4 more volume
where does T3 come from
13% thyoid
87% is deiodinated T4
what removes iodine
deiodinase enzyme
how does T3/4 work
hydrophobic and passes through cell membrane to bind to receptor, which then bind to DNA
what are thyroid hormone receptors
a and B genes: TRa1, TRa2, TRB1 (everywhere)
TRB2 (brain)
effects of THs
- Na/K ATP ase - Na out/ K in
- increased O2
- heat gen, sweating
- weight loss
- incr. resp
- increased CV
- increased metabolism
TH CNS effects
- increased dev.
- increased B-andrenergic receptors
- faster reflexes
