Regulation of Thyroid Hormone Synthesis Flashcards
Thyroid hormone is a _________-derived hormone.
tyrosine
The skeleton of thyroid hormone is ___________.
thyronine
The thyroid hormone is made hydrophobic by ___________.
its ether linkage
The full name of T4 is ________________.
3,5,3’,5’–tetraiodothyronine (also called thyroxine)
The full name of T3 is _________________.
3,5,3’–triiodothyronine
The thyroid has a copious blood supply. One of the reasons this is thought to be so is _____________.
that iodide is a trace element in water, and in the natural world we would need to absorb as much iodide from the water as possible
How is iodide absorbed by thyroid follicular cells?
By a sodium/iodide symporter (the intracellular sodium is then pumped back out through a Na/K antiporter)
The thyroid follicular cells secretes ____________ into the lumen of the thyroid.
thyroglobulin
Thyroglobulin is used entirely within _____________.
the thyroid gland
Each thyroglobulin protein contains approximately ____________ tyrosine residues that can be used to make T4.
20 (although there are many more tyrosine residues)
Thyroglobulin is made in a non-iodinated form that then gets _________________.
secreted by the thyroid follicular epithelium into the follicular colloid
Thyroglobulin gets iodinated in the ______________.
colloid and then taken up by endocytosis back into the thyroid follicular epithelium
T3 and T4 bind _______________.
nuclear receptors
Low levels of T3 induce a metabolic shift to ____________.
anabolism
High levels of T3 induce a metabolic shift to ______________.
catabolism
High levels of thyroid hormone stimulate which adrenergic receptor?
Beta-1
TSH regulates which points of thyroid production and release?
- Growth of follicular cells
- Transporters
- Thyroperoxidase
- Thyroglobulin
- Organification of iodide (putting free iodide onto protein)
- Endocytosis of thyroglobulin from the colloid
The primary constituent of the colloid is _______________.
thyroglobulin
Where is thyroperoxidase?
In the colloid, bound to the membrane
What are DIT and MIT?
Diiodotyrosine and monoiodotyrosine –these couple to form triiodothyronine
Where are T4 and T3 cleaved from thyroglobulin?
In follicular lysosomes
_____________ has a longer half-life.
T4 (another reason thyroxine is given pharmaceutically)
Why does thyrotoxicity mimic catecholamine overdose?
Because thyroid hormone potentiates the effects of catecholamines
List five effects of thyroid hormone.
- Increased basal metabolic rate
- Potentiation of catecholamine effects
- Promotes linear growth throughout childhood
- Promotes brain development throughout childhood
- Promotes anabolic effect at low doses and catabolic effect at high doses
