1
Q
How is thyroid hormone produced?
A
- Produced by vesicles, colloids are made up of a large complex glycoprotein called thyroglobulin.
- Hormones will remain bound to thyroglobulin until they are secreted from the gland.
- Upon release colloid is ingested by the thyroid cells where the peptide bonds are hydrolysed.
- Free T3 and T4 are released into the capillaries.
- Release of both these hormones from thyroglobulin is controlled by TSH.
2
Q
What is the mechanism of action of thyroid action
A
- Iodide trapping results in the uptake of iodide ion by the thyroid gland.
- Oxidised by peroxidase enzymes to form nascent iodine.
- This nascent iodine binds to tyrosine to form mono and di-iodotyrosine within the thyroglobulin.
- 2 di= T4 while mono + di = T3.
- T3 is also formed from the deiodination of thyroxin in tissues (T4).
3
Q
Calcitonin
A
- Synthesised in parafollicular C cells present in the connective tissue around thyroid follicular cells.
- Causes transfer of blood into bone by increased calcification of the bones or by diminished decalcification.
4
Q
What are the functions of thyroid hormone?
A
- Increased metabolic activity, it increases the amount of oxygen consumed in oxidative phosphorylation.
- Has an important role in growth and development of cells, in the absence of thyroid hormone GH secretion is depressed.
- Increases the rate of endocrine secretion of most glands.
-Calcitonin reduces blood calcium ion concentration (opposite function of parathyroid).
