Synthesis, Mode of action and Regulatory Effects of Thyroid Hormone- 27 Flashcards
What is a thyroid follicle
A small spherical group of cells containing a cavity.
What two hormones does the thyroid gland produce.
T3 and T4 hormones.
Where is thyroid hormones synthesised and stored.
Made in advance, precursor is stored is secretory vesicles.
What is the location of the thyroid hormone receptor
In the nucleus
What is the response of thyroid hormone binding.
Activation of genes for transcription and translation.
What is important for thyroid hormone synthesis.
Iodine must be taken in.
How is iodine transported in the thyroid.
Iodine is 20-50 times more concentrated in follicular cells than in plasma
Na/I symporter transports 2Na for every iodine ion.
Na= electrochemical gradient provides the energy for secondary active transport of iodine.
What is thyroglobulin and where is it released.
It is a glycoprotein synthesized by follicular cells and released into the colloid by exocytosis.
How is T3 and T4 synthesised on Thyroglobulin.
Tyrosine residues on thyroglobulin get iodinated by oxidised iodine giving monoiodotyrosine and diodotyrosine
Conjugation leads to adjacent tyrosyl residues being paired together
Thyroglobulin boung to T3 and T4 makes up colloid
When required the complex is taken back up into follicular cells where proteases liberate t3 and t4 release into blood
What binding proteins in the blood are T3 and T4 associated with
Thyroid hormone-binding globulin
Transthyretin
Albumin
Out of T3 and T4 what is secreted more by the thyroid gland
T4 is secreted 10x more than T3 but T3 is way more active than T4
What process converts T4 to T3
Monodeionidation of the secreted T4
How are target cells activated by thyroid hormones and where is the receptor.
Although thyroid hormone activates nuclear receptors (TR; thyroid hormone receptor) and is hydrophobic, it requires transporter proteins for movement across the plasma membrane
Hormone acts on nuclear TR, a hormone-sensitive transcription factor
What are the metabolic effects of thyroid hormone
Increased BMR
Increased oxygen consumption
Increased thermogenesis
What is the cardiovascular effects of thyroid hormones
increased cardiac output
increased heart rate and stroke volume
