Thyroid gland Flashcards
Where is the thyroid gland located?
Anterior neck between C5 and T1
Label?
What connects 2 lobes of thyroid gland?
Isthmus
What supplies thyroid gland?
Superior thyroid artery- 1st branch ECA- supply sup and ant
Inferior thyroid artery- subclavian- supply post and inf
What drains thyroid?
Middle and inferior thyroid vein
What innervates thyroid gland?
Sympathetic trunk
What controls release of hormones from thyroid gland?
Pituitary gland
How does thyroid gland form?
1) 3-4 weeks thyroid glands appear
2) Glands migrate down duct
3) Glands produce thyroxine 18-20 wks
What time period do glands start producing thyroxine?
18-20 weeks
What does thyroid gland produce?
Thyroxine- T4 (4 iodine)
Triiodothronine- T3 (3 iodine)
Which molecule is converted into what?
What enzyme?
T4 converted into T3
Via deiodinase enzymes
How are thyroid hormones synthesised?
1) TSH binds to TSH receptors
2) Iodide actively co-transported across basolateral membrane
3) Iodide diffuses to apical membrane- transported into colloid
4) In colloid thyroglobulin and tyrosine bind iodine make T1/T2
5) When thyroid stimulated T1 and T2 cleaved make T4 and T3
What is most abundant T4 or T3?
T4 (non active)
What thyroid molecule is converted into what?
T4 to T3
How is thyroid hormone secreted?
1) TRH released by hypothalamus
2) TSH released by anterior pituitary
3) TSH act thyroid gland secrete T3 and T4
4) T4 converted to T3- act target cells
Function of thyroid hormone? (3)
1) Increase metabolic rate- increase FA release, gluconeogenesis
2) Important brain maturation
3) T3 required growth hormone
