Hypothyroidism/Hyperthyroidism

Question 1

To assess for direct thyroid function, what tests would you order?

Answer 1

1. (131)I uptake
2. TSH stimulation test
3. Perchlorate discharge test

Question 2

To test for pituitary function (and thereby indirectly test thyroid function) you can order…

Answer 2

1. Serum TSH

2. TRH stimulation test

Question 3

What is the perchlorate discharge test

Answer 3

Remember that iodide must be “trapped” inside the follicular cell of the thyroid gland, and then moves to the colloid lumen to react with tyrosine via oxidation and organification rxns. Perchlorate inhibits the “trapping” of iodide inside the thyroid follicular cell and discharges it out of the thyroid. Normally, iodide is being shuttled in the colloid lumen so there is no change in the amount of iodide in the thyroid with perchorlate administration. But if there is a problem with organification of iodide, then lots of iodide will accumulate in the thyroid and get kicked out by perchlorate.

Question 4

What are 3 imaging options you have for the thyroid?

Answer 4

1. Thyroid scan (with technetium, iodine (131 or 123) or americium(241))
2. Sonography
3. X-ray