Thyroid Drugs Flashcards
What two active hormones does the thyroid gland synthesize?
T3 - more potent
T4 - converted in body to T3
What is the difference in structure between T3 and T4
T3 has 3 iodine groups, T4 has 4 iodine groups
What cells of the thyroid gland synthesize and secrete thyroid hormones?
follicular cells
What are the steps of thyroid hormone synthesis?
- uptake: and “trapping” of iodiDE
- activation: iodiDE is oxidized by peroxidase to iodiNE
- iodination of tyrosine: tyrosine is attached to the protein thyroglobulin, as mono- and di-iodotyrosine (MIT, DIT)
- coupling: MIT and DIT to form T3 and T4
Are thyroid hormones stored?
Yes, several months supply of thyroid hormones are stored in the colloid
What is involved in the release of thyroid hormones?
endocytosis and proteolysis of thyroglobulin to release T3 and T4
What happens to iodine from metabolites?
it is reutilized
What is the transport of thyroid hormones?
bound to plasma proteins
What are the plasma proteins to which thyroid hormones are bound to during transport?
thyroxine-binding globulin
transthyretin
What form of thyroid hormone is active?
free form
What is the metabolism of thyroid hormone?
peripheral deiodination ( reutilization of iodine)
and conjugation
How are thyroid hormone excreted?
via the bile
T3 is ….
-LESS protein bound
(higher % is in free form)
-more RAPIDLY metabolized (shorter half life)
-more POTENT
-physiology effects are due to T3
T4 is ….
-MORE protein bound
-more SLOWLY metabolized (longer half-life; high protein binding of T4 slows its degradation)
-LESS potent
-most of thyroid hormone in blood is T4
Most of the thyroid hormone that is secreted by the thyroid is T_
4
T3 and T4 act of the ____ receptor and cause the ____ effects
Same, same
What is the T3/T4 receptor?
nuclear transcription regulator (regulates specific thyroid hormone response elements in DNA)
The following are activities of _____ hormones:
1. Stimulation of growth and development (physical and mental)
2. Stimulation of metabolism (synthesis and degradation are increased)
3. Increased heat production and O2 consumption due to metabolism
4. Increased sympathetic activity to support metabolism
5. Increased HR, CO, vasodilation, blood flow
6. Diverse targets
7. Long term effects
Thryoid
Treatment of hypothyroidism includes ___ ________ and ________ methods
non-pharmacologic (diet)
pharmacologic (replacement thyroid hormones)
What are the 2 dietary changes that help treat hypothyroidism?
- adequate iodine in diet
- avoid foods with “goitrogens”
____ therapy for cretinism and adult hypothyroidism
oral
__ plus supportive therapy in ER for myxedema coma
IV
is replacement therapy life long?
yes, but some remissions occur
Oral therapy for hypothyroidism is
effect, cheap, easy, painless and safe