Thyroid/Anti-Thyroid Agents Flashcards
1
Q
thyroxine (T4, Synthroid)
A
Thyroid hormone- synthetic
- act as agonist of thyroid hormone receptor (same effects as natural hormone)– inc. BMR, inc. HR and CO, stimulate protein synthesis
- used in treatment of hypothyroidism
- can be given oral, IM or IV
- children and pregnant women require higher dosing
- *potency of 1, half-life of 7 days, less expensive
- converted to T3 in peripheral tissues
- S/fx: thyrotoxicosis (nervousness, insomnia, increased BMR), stressful on CV system
- use cautiously in pts with CV disease and pregnant women
2
Q
triiodothyronine (T3, Cytomel)
A
Thyroid hormone- synthetic
- act as agonist of thyroid hormone receptor (same effects as natural hormone)– inc. BMR, inc. HR and CO, stimulate protein synthesis
- used in treatment of hypothyroidism
- can be given oral, IM or IV
- children and pregnant women require higher dosing
- *potency of 4, half-life of 1 day, more expensive
- S/fx: thyrotoxicosis (nervousness, insomnia, increased BMR), stressful on CV system
- use cautiously in pts with CV disease and pregnant women
3
Q
T4 + T3 (Thyrolar)
A
Thyroid Hormone
- act as agonist of thyroid hormone receptor (same effects as natural hormone)– inc. BMR, inc. HR and CO, stimulate protein synthesis
- used in treatment of hypothyroidism
- can be given oral, IM or IV
- children and pregnant women require higher dosing
- T4 is converted to T3 in peripheral tissues
- S/fx: thyrotoxicosis (nervousness, insomnia, increased BMR), stressful on CV system
- use cautiously in pts with CV disease and pregnant women
4
Q
propylthiouracil (PTU)
A
Thioamide (thioureylene)- Oral tx for hyperthyroid
- inhibits thyroid peroxidase thus decreasing the oxidation of iodide, the iodination of thyroglobulin, and the coupling of MIT and DIT to form T3 and T4
- also inhibits the peripheral conversion of T4 to T3
- initial time course of action takes weeks b/c thyroid hormone stores must be depleted first
- S/Fx: skin rash, delayed hypothyroidism, agranulocytosis (not common but dangerous)
- works faster then MMI, but less potent and shorter DOA
- used in pregnant women during first trimester
- can be used in lactating mothers
- initially high doses that are tapered down
- need to observe for 12-18 months
5
Q
methimazole (MMI)
A
Thioamide (thioureylene)- Oral tx of hyperthyroid
- inhibits thyroid peroxidase thus decreasing the oxidation of iodide, the iodination of thyroglobulin, and the coupling of MIT and DIT to form T3 and T4
- initial time course of action takes weeks b/c thyroid hormone stores must be depleted first
- S/Fx: skin rash, delayed hypothyroidism, agranulocytosis (not common but dangerous)
- more potent and longer DOA then PTU
- usually tried first but cannot use in first trimester of pregnant mothers-can be used in lactating mothers
- initially high doses that are tapered down
- need to observe for 12-18 months
6
Q
potassium iodide
A
- oral tx of hyperthyroid
- inhibits release of T3 and T4
- time course of action is fast (days) but effects are transient (2-8 weeks)
- not rarely used alone
- S/Fx: readily reversed by discontinuing use, rashes, swollen salivary glands
- also used to prevent uptake of iodine 131 after nuclear accident
7
Q
radioactive iodine
A
- oral treatment of hyperthyroidism
- concentrates in thyroid and causes localized radiation damage
- S/Fx: delayed hypothyroidism, radiation exposure
- time course of action is slow (weeks)
- do not use in pregnant women or nursing mothers
- can cause exacerbation of hyperthyroidism as thyroid is destroyed (causes massive release of hormone)
8
Q
propranolol
A
Beta-adrenergic antagonist
- used to alleviate symptoms associated with inc. CV activity
- thyroid hormones inc. sensitivity of CV receptors to catecholamines
9
Q
reverse T3
A
-biologically inactive thyroid hormone
10
Q
thyroid follicular cell
A
- thyroid cells that surround amorphous colloid center
- endocytosis of thyroglobulin from colloid
- T3 and T4 is hydrolyzed from larger complex and free T3 and T4 diffuses into blood stream
11
Q
thyroglobulin
A
- large complex of MIT, DIT that combines with iodine to form bound T3 and T4
- stored in colloid of thyroid
- hydrolyzed to form free T3 and T4
12
Q
MIT/DIT
A
-bound within larger thyroglobulin complex and forms T3 and T4 when iodine binds to it
13
Q
TBG (thyroxine binding globulin)
A
- large protein that binds T3 and T4 and helps transport through blood stream
- only free T3 and T4 are active
14
Q
thyroid peroxidase
A
-within membrane that separates follicular cells and colloid of thyroid, oxidizes iodide to form iodine which is required to form T3 and T4 on thyroglobulin complex
15
Q
primary hypothyroidism
A
- due to dysfunction of thyroid gland itself
- low T3, T4; high TRH and TSH
- AKA Hashimoto’s disease
