Thyroid Function Test

Question 1

Hyperthyroidism may present with what TSH lab values? How about T4?

Answer 1

DECREASED TSH

INCREASED Free T4

Question 2

Which is more biologically active between T3 and T4?

Which has a longer half-life?

Answer 2

T3 (T3 is also in greater circulation)

T4 has a greater half life however; keep in mind when attempting to achieve steady state

Question 3

How will HYPOthyroidism present with lab values? TSH and Free T4?

Answer 3

INCREASED TSH

DECREASED T4

Question 4

If you receive a TSH above what value; Tx is indicated? What is the “subclinical” criteria?

Answer 4

> 10 TSH you must treat

6-8 subclinical

Question 5

What are the only two labs you generally need to order for thyroid?

Answer 5

TSH

Free T4

Question 6

When would a Serum Thyroglobulin Level be useful? (even though rarely used)

Answer 6

FACTITIOUS HYPERTHYROID from exogenous sources

Question 7

What are some potential causes of ELEVATED Serum T4?

Answer 7

Graves
Transient HYPERthyroidism
Toxic adenoma
Toxic multinodular goiter

Rarer causes SLIDE #