Flashcards in LMP301 Lecture 8: Thyroid Disease Deck (82)
What is symptom of goiter?
Enlarged thyroid gland
Is goiter due to hypo, hyper, or eu-thyroid?
Can be anything
Goiter is due to...
Lack of iodine
Thyroid gland secretes...
T3 and T4
What is more abundant in the blood, T3 or T4?
What makes 2/3 of the circulating T3?
Peripheral tissues (liver, kidney) deiodinate T4
What stimulates the production of thyroid hormones?
What is more biologically active, T3 or T4?
What is the inactive form of T3?
How is rT3 produced
metabolised from T4
(T4 can make both T3 and rT3)
How can local thyroid status be modulated?
Balance production of T3 and rT3
Thyroid hormones are needed for...
all tissue maturation and metabolism
Precursor for thyroid hormones
1 iodide attached to tyrosine
2 iodides attached to tyrosine
T4 is made up of
DIT + DIT
T3 is made up of...
MIT + DIT
T4 - 1 iodine (at first benzene)
rT3 is made up of...
T4 - 1 iodine (at second benzene)
T4 is also called...
Hypothalamus-pituitary-thyroid axis for T3, T4 control
a. pituitary: TSH
Thyroid: TSH binds on TSH receptor -> T4 and T3 production
Feedback of thyroid hormones
TSH neg feedback on hypothalamus (short loop feedback)
T4 + T3 neg feedback on hypothalamus, a. pituitary (long loop feedback)
How do thyroid hormones travel? Give some examples.
Bound to carrier proteins in plasma (e.g. albumin, TBG)
Which thyroid hormones are active?
The ones not bounded to carrier proteins in the plasma
% of free T3 + T4
T3: 0.3% of all T3
T4: 0.03% of all T4
What may change the concentration of free thyroid hormones?
Changes in the [ ] or affinity of carrier proteins
Are FT3 + FT4 better or worse markers of thyroid function? Why?
Effects of increasing TBG
More T4 + T3
What compounds increase TBG?
- oral contraceptives