Thyroid Physiology Flashcards
Follicular cells surround which structure?
Colloid
What is found in the colloid?
Tyrosine-containing thyroglobulin
What other cell is found in the thyroid gland?
Parafollicular C cells
What happens when iodine is taken up by follicle cells?
It attaches to tyrosine residues on thyroglobulin to form MIT and DIT
MIT and DIT combine to produce what?
T3
DIT and DIT combine to produce what?
T4
T3 is the active thyroid hormone. True/false?
True
90% of thyroid hormone secreted is T3. True/false?
False - T4
What are the major sites of conversion of T4 to T3?
Liver and kidney
What plasma proteins will bind to T3 and T4?
Thyroxine-binding globulin
Transthyretin
Albumin
Only unbound T4 and T3 is active. True/false?
True
T3 and T4 cause a decrease in metabolic rate and thermogenesis. True/false?
False - increase
Why is propranolol used in the early stages of hyperthyroidism?
As thyroid hormones increase the number of receptors to adrenaline and noradrenaline
Outline the HPT axis
Hypothalamus releases TRH which stimulates anterior pituitary to release TSH stimulating thyroid to release T3 and T4
What subfamily of enzymes are important in activation and deactivation of thyroid hormone?
Deiodinase
