Thyroid hormone plays a major role in the development of a fetus. According to a recent study , abnormal levels of the natural hormone can be toxic to a developing fetus. In some cases, a woman can have high levels of thyroid hormone and still be normal because of thyroid resistance. Yet, these affected women may carry fetuses that have been exposed to high thyroid hormone levels.
Researchers studied extended members of a large family in which both parents were unaffected, or either the mother or the father had high levels of the hormone but was thyroid resistant. Results showed affected mothers had an increased rate of miscarriage or a higher chance of having an underdeveloped child if they carried their baby to term.
Thus researchers say their data shows, for the first time in humans, that high levels of thyroid hormone can exert a direct toxic effect on fetal development. Researchers say they hope that this study will emphasize the importance of accurate thyroid replacement for pregnant women with low thyroid levels, because over replacement can be dangerous to the well being of mother and child.