Thyroid Gland Flashcards
Reaction to Make T3, T4
Iodide+H202=I2
I2+Tyrosine=MIT or DIT
Two DITs make T4
-A lot more produced than T3
DIT+MIT=T3
Conversion of T4–>T3
Need Deiodinase
-converts to active form of T3 (some can be inactive form)
When is the formation of T3 favored?
When availability of iodine is restricted
Pedrin Within Throid hormone syntesis
Pedrin pumps out I2 so it can interact with MIT and DIT to make T3/T4
Mutation of Pedrin also affects the cochlea and can cause a goiter
PTU effects?
Treatment for hyperthyroidism by blocking peroxidase activity
Can also use perchlorate/thiocynate to not allow I to be brought into cell
What protein is the main transporter of T3/T4?
TBG
-has higher affinity for T4 even though T3 has more profound effects
Clinical Signs of 1 Hyperthyroidism
Increased T4, increase T3 resin uptake
TSH is low!
-due to negative feedback of T3
Clinical Signs of Hypothyroidism
T4 decrease and decrease use of T3 resin
Cold, fatigue, muscle weakness, weight gain
High TBG/Pregnancy
Increase TBG, T4, but low T3 resin uptake
Low TBG caused by hepatic failure
Low T4, but high T3 resin uptake
Actions of TSH on Thyroid Gland
TSH binds to G protein, making cAMP
cAMP causes more I to come into cell so more thyroid hormone is made
Wolff-Chaikoff Effect
Excessive I- intake puts brakes on perioxidase activity
Actions of Thyroid Hormone
Growth of bones,
Maturation of CNS,
Increase CNS
Increase Metabolism
-increase Na/K ATPase, increase in O2 use
Increase Cardiac output
-T3, and increase of B1 receptors on heart
What two symptoms do patients with hypothyroidism exhibit due to Vit A and Cholesterol?
High blood cholesterol and can suffer from blindness and jaundice due to inability to break down Cholesterol and Carotene
Secondary Hyperthyroidism
Causes increase in TSH levels from pituitary
