New studies—false neg. preg test in thyroid patients

Thyroid & pregnancy:

High levels of thyroid antibodies are associated with decrease response of thyroid gland to HCG in early pregnancy.

The highest levels of hCG are seen in the first trimester. This hormone can also bind to the thyroid gland and stimulate it, similar to TSH but much weaker. During pregnancy, hCG stimulates the thyroid gland of the pregnant mother to make more thyroid hormone, which is important for normal development of the baby. TSH levels in the mother decrease as hCG levels rise. However, if the mother has autoimmune thyroid disease with high levels of antibodies to thyroid gland, such as thyroid peroxidase antibody (TPOAb) or thyroglobulin antibody (TgAb), the thyroid gland may not respond as well to hCG. Because of this, TSH levels may not decrease as much as would be seen in the absence of these antibodies. This study was done to assess response of thyroid gland

to hCG in pregnant women with and without thyroid antibodies during the first 20 weeks of pregnancy.

For more here is a link below.

https://www.thyroid.org/wp-content/uploads/publications/ctfp/volume12/issue6/ct_public_v126_11_12.pdf