4.3 Endocrine Flashcards
TSH stimulates all activities of the ______ except?
thyroid EXCEPT storage
TSH stimulates what 4 main activities?
1) thyroglobulin synthesis in follicle
2) iodid trapping by follicle
3) conversion of iodide to iodine (peroxidase)
4) iodination of tyrosines of thyroglobulin
storage of iodinated thyroglobulin is in?
colloid
TSH made/secreted by?
anterior pituitary
targets thyroid follicle
what AA is iodated to make T3 and T4?
tyrosine
iodide or iodine is used to iodinate thyroglobulin?
iodiNe
Why doesn’t TSH promote storage?
bc once we make T3 or T4 we don’t want them to STAY in the colloid, we want them taken back up by the follicle and released into blood
What is MIT?
monoiodotyrosine= tyrosine with ONE iodine bound
what is DIT?
diiodotyrosine= tyrosine with TWO iodines bound
both MIT and DIT remain linked to thyroglobylin while in the ____?
colloid
*Not until thyroglobulin is taken out of colloid back into follicle by penocytosis does LYSOSOMAL PROTEASE start breaking bonds to release T3 or T4
roles of peroxidase?
1) convert iodide to iodine
2) coupleing of MIT and DIT into T3
and DIT and DIT into T4
3)attachment of iodine to thryroglobulin
TSH > pinocytosis of _______ > degradation by ________ > T4 and T3 released into cytoplasm and then into circulation
- TSH
- pinocytosis of colloid droplets
- degradation by lysosomal protease
- T4 and T3 released into cytoplasm
- T4 and T3 into circulation
T4 conversion to T3 happens where?
liver
90% of intracellular (in cell) thyroid is?
T3
90% of thyroid hormone coming out of the thyroid is?
T4
thyroid hormones are _____ of cellular activity? explain
modulators
*increase metabolic activity and play essential role in growth and development
any issue with iodine causes?
Explain how
global detramental affects bc thyroid hormones affect so many cells
*hypothyroidism
=decrease iodine > can’t make T3/T4 > decrease - feedback inhibition of hypo and pit > increase TSH levels > excessive stimulation of thyroid = goiter
thyroid hormones diffuse through cells membranes why?
so they canbind on chromatin and alter transcriptions, translation, and protein synthesis
thyroid hormones bind to receptors on?
chromatin
explain the regulation of thryoid hormone?
> TRH > anterior pituitary > TSH > thyroid > T4/T3
***- feedback important
what is the most important regulator of thyroid hormone
negative feedback
the cold stimulus of the hypothalamic temperature regulatory center influences what function?
thyroid function
- in human infants and other mammals (minimal or nonexistent in adults)
- hypothalamic secretion of TRH is initiated via neuroendocrine reflex involving peripheral cold receptors
neuroendocrine reflex involves?
peripheral cold receptors of the hypothalamis; can initiate TRH secretion
how does stress affect thyroid hormone secretion?
stress increases cortisol > inhibition of hypothalamus > decrease TRH, TSH, and T4/T3
main role of cortisol
regulate hormone levels in the blood (brings nutrients out of storage)
*also inhibits TSH secretion
hypothyroidism
inadequate secretionof thyroid hormones
hyperthyroidism
oversecretion of thyroid hormones
both hyperthyroidism and hypothyroidism results in?
goiter
what is goiter
thyroid hypertrophy
hypothyroidism causes
1) tumor = compressing some structure within the hypothalamus/ ant pit/ thyroid axis
2) iodine deficiency (most common)
- –usually endemic to a particular region of the world
how does USA avoid endemic goiter?
we put iodine in salt to avoid hypotheyroidism
effects of hypothyroidism?
decreasedmetabolic rate less heat production proteun synthsis nutrient utilization oxygen consumption synaptic acitivty
general symptoms of hypothyroidism?
weight gain
decreased cold tolerance, growth rate, repisration, heart rate, cardiac output, altertness
why would hypothyroidism decrease tolerance to cold?
bc lower metabolic rate so less heat production
what is cretinism?
hypothyroidism in children/infants
why is cretinism such a big deal?
child becomes short of stature, gains weight and can have mental retardation issues if not treated
what does cretinism effect orally?
delayed primary tooth eruption, enamel hypoplasia, macroglossia
*large tongue
define macroglossia
enlarged soft tissue; accumulation of mucopolysaccarrides in soft tissue
what is myxedema?
hypothyroidism in adults; enlarged soft tissue
hypothyroidism in adults symptoms?
- myxedema
- dry and/or loss of hair
- subnormal body temperature, hoarse voice, muscle weakness, slow tendon jerk
