The Thyroid Gland Flashcards
What are the 2 main hormones released by the thyroid gland?
T3 - Triiodothyronine
T4 - Thyroxine
What are the thyroid follicles made of ?
Walls of follicular cells and C cells with colloid in the middle
What is found within the C cells within the thyroid ?
Calcitonin (Ca regulating hormone)
How does iodine enter the follicular cells ?
Through the Na/I transporter.
This coupling enables follicular cells to take up iodine against a concentration gradient
How many tyrosine and iodine make up T3 ?
2 Tyrosine
3 Iodine
How many Tyrosine and Iodine make up T4 ?
2 Tyrosine
4 Iodine
Movement of TH from the colloid into the plasma is influenced by what ?
TSH release from the pituitary gland
The majority of circulating TH is found ______ to a plasma ______ known as _____ _______ _______ (TBG).
bound
Protein
Thyroid Binding Globulin
What affect does protein binding have on the half life of the hormone T4 ?
Extends the half life
What are the half lives of T3 and T4 ?
T3 ~1 day
T4 ~6 days
The majority of circulating TH is T3 or T4 ?
T4
The intracellular receptors bind to which form of TH more?
T3
Which is more physiologically active, T3 or T4?
T3 - more binding with intracellular receptors
What are the main symptoms of Hyperthyroidism?
Weight-loss Heat intolerance Muscle weakness Hyper-excitable reflexes Increased HR
What are the main symptoms of Hypothyroidism?
Weight gain Cold intolerance Brittle nails Thin skin Slow speech Slow reflexes Fatigue Slow HR Weak pulse
