Thyroid Hormones Flashcards
(39 cards)
Within the thyroid gland, thyroid hormone is produced by _ cells, and stored bound to _
Follicle cells
Thyroglobulin
Parafollicular cells produce _
Calcitonin
Within the thyroid, DIT and MIT are used to make _ (3)
T3, T4 and reverse T3
Iodine trapping within the thyroid require wha transport protein?
Na/I symporter
Iodide ions are converted to iodine by _
Thyroid peroxidase
What is the organification step of thyroid synthesis?
Oxidized iodine binds tyrosine AA residues on thyroglobulin to make DIT or MIT
What is stored as colloid in the follicle lumen?
Iodinated thyroglobulin, NOT T3 or T4
Free MIT and DIT are deiodinated by _, freeing iodine for reuse
Deiodinase enzyme
T3 and T4 are transported in the blood stream bound to _. How are they delived to the CNS? Majority of thyroid hormone released is _? Why?
Thyroxine binding globulin
Transthyretin
T4 - longer plasma half life
Where are thyroid receptors located?
Nuclear receptor
The major regulator of thyroid release is _. What are the effects of somatostatin and dopamine?
TSH
Both inhibit TSH release
increased thyroglobulin proteolysis, increased Iodide pump activity, increased organisfication, increase size, activity and number of thyroid cells are mediated by _
TSH
If a patient has low TSH, what would you expect upon inspection of the thyroid cells?
Low TSH - High amounts of colloid (b/c not released), flat follicular cells
An iodine deficiency can lead to _.
Goiter. Thyroid cell proliferation
The first effect of TSH on the thyroid cells is _
Binding surface GPCR
Increased cold and increased caloric intake lead to _
Increased TSH release
A diet high in iodide lead to _
High blood iodide levels, reduced trapping of iodide by thyroid, decreased size and decreased blood supply
The active form of the thyroid hormone is _. How does it bind DNA?
T3
As a T3-RXR heterodimer (vs. steroid hormones homodimerize)
Know that T3 is able to bind ribosomes, mitochon, plasma mem. to mediate non-genomic responses
done
T4 is converted to T3 by _
Mono-deiodinase
In the absence of T3 binding, what is the action of the T3 receptor?
It is able to bind DNA and repres gene transcription, unlike the steroid hormone sequestered by HSP90
The major effect of thyroid hormone is _
Increase in metabolic rate
How does thyroid hormone affect proteins?
Increases protein catabolism, too much can lead to muscle breakdown / weakness
Regarding linear growth, fetal brain development and tooth/hair development, what is the role of thyroid hormone?
Required for all.
Reduced fetal thyroid = poor outcome for fetus
Low thyroid post birth = dry brittle hair
