Thyroid Flashcards
What are the building blocks of thyroid hormone throughout evolution
Tyrosine and iodine
What does the iodination of tyrosine produce
Mono-iodotyrosine
Di-iodotyrosine
What are the full names for T3 or T4
T3= liothyronine T4= thyroxine
Do mammals have a follicular thyroid gland or a endostyle
Follicular thyroid gland
What protein do humans use to organify iodine
Thyroglobulin
Where does digestion of thyroglobulin occur in humaan
in the gland itself
What are the roles of thyroid hormones in fish
High T4 levels triggers the move from fresh water to salt water
What does T4 cause in lizards
Stimulation of metabolism in lizard when external temperature gets to 32 degrees
How much does the thyroid gland weigh in the adult
15-20g
What are the dimension of a thyroid lobe
2cm thick
4cm long
Which lobe of the thyroid is usually larger
right lobe
Which gland has the highest blood supply in the body
Thyroid
What is the rate of blood supply to the thyroid
4-6ml/min/g
Briefly describe the blood supply to the thyroid
Comes from superior thyroid (from the external carotid) and the inferior thyroid (from subclavian)
What is the role of parathyroid hormone
Maintaining calcium homeostasis
What do the C cells in the parathyroid produce
Carcitonin
Why is carcitonin useful clinically
Marker of medullary thyroid cancer which arises from C cells
Where do the thyroid and associated structure arise from
Pharyngeal arches
Briefly describe the microanatomy of the thyroid gland
Layer of follicular thyroid cells surrouding a lumen that is filled with clear, proteinaceous colloid
How do follicular cells change histologically when the thyroid becomes more active
Changes from cuboidal to columnar when more active
Where does the TSH receptor receive signals from
Pituitary gland
How many follicular cells are there per lobule? How many arteries supply each one
20-40
1 artery
What family of receptor in TSH-R receptor?
G protein coupled receptor
What does TSH stimulate the expression of?
NIS, TOP, Tg and generation of H202
Effect of TSH on T3: T4 ratio
Increases amount of T3 relative to T4
Describe iodide uptake into the follicular cell
Iodide taken up by NIS
Transferred to the colloid
Oxidised by TPO
What % of t4 is iodide by weight
65%
