Thyroid Hormones

Question 1

What may suggest an increased release of thyroglobulin into plasma?

Answer 1

• thyroiditis
• nodular goiter
• cancerous thyroid tissue

Question 2

What molecules can you deiodinate to recycle I- and Tyr?

Answer 2

MIT and DIT

Question 3

How do you get the most circulating T3?

Answer 3

Activation via 5’ monodeidinase from T4 (thyroxine)

Question 4

What is the low T3 syndrome? Why does it occur?

Answer 4

• enhanced conversion T4 ▶️ rT3
• fasting, medical and surgical stress, catabolic diseases, ⬆️⬆️ cortisol

*results: ⬇️ metabolic rate, conserve energy resources

Question 5

Why does a hypothyroidism patient suffer of night blindness and yellowing of the skin?

Answer 5

Thyroid hormone required for carotene ▶️ vitamin A

Question 6

How do the thyroid hormones make the negative feedback to the TSH secretion?

Answer 6

Mainly T4 ▶️ reduce the sensitivity of the thyrotroph (anterior pituitary) to TRH ▶️ ⬇️ TSH

Question 7

What is the Wolff-chaikoff effect?

Answer 7

Secondary hypothyroidism because high iodine intake

Question 8

Which are the only type of thyroid disorder that have increased radioactive iodine uptake?

Answer 8

• grave’s disease

- toxic nodular goiter

Question 9

Why if subacute thyroiditis and “silent” or “painless” thyroiditis are hyperthyroidism cause, don’t increase radioactive iodine uptake?

Answer 9

They are “leaking” thyroid hormone out of the gland damaged by antibodies