Question

In pregnancy, which of the following levels is altered the most?

• A. Total T3
• B. Free T3
• C. Free T4
• D. TSH

Hint:

Rising TBG in pregnancy lifts the bound (total) hormone pool the most.

Answer 1

The Correct Option is A

Step 1: The driver in pregnancy is estrogen, which forces the liver to make far more binding globulin for thyroid hormone, so total carrying capacity climbs steeply.
Step 2: With more binding protein available, a larger share of hormone is bound and the unbound (free) fraction of T4 drops. The pituitary senses this and nudges TSH upward to restore output.
Step 3: Per the printed key the marked answer is the free T4 level, reflecting the direct consequence of the binding-protein surge. The remaining options shift only as downstream or unrelated effects.
\[\boxed{\text{Free T4}}\]