Results
What are the changes in thyroid function
during normal pregnancy?
As pregnancy is a high estrogenic state, serum thyroxin
binding globulin (TBG) increases and results in high
serum total T4 and T3 concentrations. During the first
trimester, the serum hCG level rises continuously and
peaks near the end of the first trimester. The stimulating
effect of hCG on the TSH receptor causes a fall in serum
TSH levels in the first trimester of pregnancy (11, 12).
Being aware of the changes regarding serum FT4, TSH
and hCG levels throughout pregnancy would be helpful
for interpretation of thyroid function test in hyperthyroid
mothers (Fig. 1) (11).