Thyroid Hormones Flashcards
What are thyroid hormones derived from?
Tyrosine residues within the protein thyroglobulin
What are the thyroid hormones?
T4 (thyroxine) which is then turned into T3
Where are the thyroid hormones synthesised?
In the thyroid gland
How is the thyroxine molecule (T4) made?
- Thyroid gland cells concentrate iodine for thyroid hormone synthesis
- Tyrosine molecules on the protein thyroglobulin are iodinated
- The iodotyrosine molecules in the thyroglobulin are cross-linked
- The thyroxine molecule is cut out of the thyroglobulin
How and where is T3 derived from T4?
T3 is produced in the peripheral tissues through the deiodination of T4
Are thyroid hormones hydrophilic or hydrophobic?
Hydrophobic
What do thyroid hormone receptors bind to?
Thyroid hormone response element (TRE) - recognition sequence in double-stranded DNA
What type of receptor is a thyroid receptor?
Nuclear receptor
When are thyroid hormone receptors bound to thyroid response elements (TRE) in DNA?
Both in presence and absence of hormone
In the absence of hormones, what does that receptor bind?
Repressor molecules
In the presence of hormones, what does there receptor bind?
Repressor leaves, co-activator binds to receptor and transcription starts
What is the difference between thyroid and steroid hormone receptors?
Thyroid hormone receptors are always bound to DNA
- Steroid hormone receptors pick up their steroid molecule and then bind to DNA
- Thyroid hormone receptors pick up their hormone, there is a change that happens in the receptor that results in transcription of mRNA and a new protein being made
What is it called when thyroid hormone receptors bind with each other?
Homodimer
What is it called when thyroid hormone receptors bind with other nuclear receptors?
Heterodimer
