Blood levels of hCG, TSH, free thyroxine (FT4), TPOAb, and TgAb were measured when they enrolled in the study. Pregnant women were divided into 4 groups: group 1 had both TPOAb and TgAb, group 2 had TPOAb only, group 3 had TgAb only, and group 4 did not have TPOAb or TgAb. There were 128 pregnant women in group 1, 90 women in group 2, 188 women in group 3, and 416 women in group 4. For group 2 and group 3, pregnant women were further divided into three groups each, from lowest level of thyroid antibody to highest level of thyroid antibody.
Higher hCG levels correlated with lower TSH levels in all groups. However, hCG level did not correlated with TSH levels in pregnant women with highest levels of TPOAb in group 2 and in pregnant women with highest levels of TgAb in group 3. Higher hCG levels correlated with higher FT4 levels in group 2 and group 4, but not in group 1 (pregnant women with both TPOAb and TgAb). However, hCG level did not correlated with FT4 level in pregnant women with highest levels of TgAb in group 3.
WHAT ARE THE IMPLICATIONS OF THIS STUDY?
In pregnant women with normal TSH levels in pregnancy, high levels of thyroid antibodies, including TPOAb and TgAB, were associated with decreased response of thyroid gland to hCG. The findings of this study suggest that having high levels of thyroid antibodies may interfere with increased thyroid hormone production caused by high levels of pregnancy hormone in early pregnancy. More studies are needed to confirm the findings of current study and to study possible effects of high levels of thyroid antibody in pregnancy with normal TSH levels.
— Sun Lee, MD