254. Thyroid physiology

Question 1

What are the two hormones the thyroid produces?

Answer 1

T3-Triiodothyronine

T4- Thyroxine

Question 2

What is the role of T3 and T4?

Answer 2

Both circulate in plasma however T3 is more physiologically active

They both provide negative feedback as well as raising metabolic rate and promote thermogenesis typically via catabolism and anabolism.

Question 3

What long term effects do thyroid hormones have?

Answer 3

Critical for growth

Essential for brain development in utero

Question 4

What else inhibits thyroid function?

Answer 4

Glucocorticoids- inhibit TSH and conversion of T4 to T3

Somatstatin- Inhibits TSH and conversion of T4 to T3

Question 5

Discuss the micrscopic structure of thyroid hormone?

Answer 5

Contains follicles- spherical structures lined by follicular cells and contain colloid in the centre with 2-3 months of TH

2 cell types- clear cells- secrete calcitonin
Follicular cells- support thyroid hormone synthesis

Question 6

What do you need to make thyroid hormone

Answer 6

Tyrosine and iodine- combine

Thyroid peroxidase- catalyst

Question 7

How do the thyroid hormones circulate in the plasma?

Answer 7

T3 and T4 circulate mostly bound to proteins

T4 has a higher half life than T3 but must be converted into T3 to be physiologically active.