Flashcards in Thyroid Function in Health and Disease Deck (59)
What are the functions of the thyroid gland?
Secrete thyroid hormones > regulate metabolism
Secrete calcitonin > regulate Ca levels
What is the structure of the thyroid gland?
2 lobes joined by isthmus
What is the location of the thyroid gland?
Anterior in neck
What cells surround the colloid?
Where is thyroglobulin located?
Where are the C cells?
In interstitial spaces
What is the function of C cells?
How are thyroid hormones synthesised?
1. Follicular cell synthesises enzymes and thyroglobulin for colloid
2. Na/I symporter brings iodide into cell > pendrin transporter moves iodide into colloid
3. Enzymes add iodine to tyrosine > make T3 and T4
4. Thyroglobulin taken back into cell in vesicles
5. Intracellular enzymes separate T3 and T4 from protein
6. Free T3 and T4 enter circulation
What is the role of thyroglobulin?
Stops iodine from diffusing out
Where do we get our iodine from?
What are the uses of iodine in the body?
Thyroid hormone synthesis
What are the structural components of thyroid hormone?
What are the proportions of T3 and T4 made by the thyroid gland?
T3 = 10%
T4 = 90%
How much T3 is derived from T4?
Why are thyroid hormones bound to plasma proteins?
Where is thyroid stimulating hormone (TSH) released from?
What does TSH do?
Stimulates all steps in thyroid hormone synthesis
Where is thyroid releasing hormone (TRH) released from?
What increases levels of TRH secretion?
Cold in infants only known factor
What decreases levels of TRH secretion?
What is the half-life of T4?
What is the half-life of T3?
What are the factors affecting release of thyroid hormones?
What are the target tissues of thyroid hormones?
Most cells of body
What are the actions of thyroid hormones?
Increase basal metabolic rate and oxygen consumption
- Increases HR
- Increases CO
Is thyroid hormone essential for life?
No, but essential for child growth and development
How does thyroid hormone promote growth?
After birth, essential for GH and IGFs actions
When is thyroid hormone needed for nervous system development?
Before and after birth
When does goitre occur?
In both hypothyroidism and hyperthyroidism