Thyroid Disorders and Birth Defects: Uncovering the Truth

Although the health impacts of thyroid disorders can be severe and wide-ranging, most thyroid-related illnesses and diseases can be controlled with close medical supervision. For many thyroid patients, the prospect of a long, healthy life is a realistic and achievable dream.

For infants of women with thyroid disorders, though, the outlook is often not so rosy. The thyroid is a key component of the endocrine system, which controls the release and regulation of hormones. During pregnancy, the mother’s endocrine system releases the hormones that control the growth and development of the fetus.

Because women with thyroid disorders often experience significant variances and fluctuations in endocrine system function, their ability to support a normal pregnancy can sometimes be affected. This week, we will take a look at the troubling link between thyroid disorders and birth defects.

The Role of Hormones in Pregnancy

The changes that transform a handful of cells into a fully-formed human infant in the span of just 40 weeks are nothing short of miraculous. In order to ensure that fetal development occurs properly, there are literally thousands of physical mechanisms and processes that must take place, and the chemical compounds known as hormones are responsible for igniting and sustaining many of these processes.

Because the thyroid gland is one of the most important organs in the hormone regulation process, any level of thyroid dysfunction can result in insufficient or excessive release of hormones during pregnancy. In many cases, women with severe thyroid disorders often experience difficulty becoming pregnant, or they may not be able to sustain a pregnancy to full term. However, when women with thyroid disorders do carry a pregnancy to full term, their infants bear an increased risk of certain birth defects, all of which are related to the improper regulation of maternal hormone levels during pregnancy.

Maternal Thyroid Disorders and Birth Defects

Although there are a range of birth defects that have been linked to maternal thyroid disorders, the most serious potential problems are related to neurological deficiencies in the infant. The mother’s thyroid gland plays a particularly important role in guiding the brain development of the growing fetus during pregnancy, and as such, when a thyroid disorder has limited the endocrine system’s ability to function normally, the fetus’ brain development processes can be interrupted.

The most serious outcome of maternal thyroid disease is mental retardation in the infant. In fact, in parts of the developing world in which iodine deficiency is a widespread problem, many women who suffer from severe hypothyroidism as a result give birth to infants with a unique form of mental retardation. Although iodine deficiency is not a chief cause of thyroid disorders in the United States and other developed nations, some mothers with severe hypothyroidism that has remained untreated still give birth to infants with mental retardation and other related types of neurological birth defects.

The link between severe hypothyroidism and the risk of birth defects has long been established. In more recent studies, scientists have attempted to gauge the impact of milder forms of thyroid disorders on pregnancy. Although the difficulties of properly diagnosing, detecting, and treating low-level thyroid disorders have made this course of study challenging, recent investigations have identified a number of risks among women with milder thyroid disorders and their infants.

Problems that have been cited in the research literature include a higher risk of premature delivery, diminished intelligence and IQ in childhood, heart problems, cleft palate, cleft foot, kidney disorders, and nervous system disorders. In one study conducted by scientists at John Hopkins University, it was found that women with mild to severe cases of hypothyroidism, hyperthyroidism, and other forms of thyroid disease had an 18% chance of bearing infants with some form of birth defect or developmental disorder. In the general population, the risk of birth defects is calculated at 3%, so it is clear that the presence of maternal thyroid disorder seems to significantly heighten the risk of birth defects.

Thyroid Prevention and Treatment During Pregnancy

Although these figures can sound daunting, the good news is that advances in medical technology have made the process of treating women with thyroid disorders during pregnancy much more effective in recent years. With constant monitoring throughout pregnancy, there is a very good chance that thyroid hormone fluctuations can be kept within a small range, allowing for proper fetal growth and development. Millions of healthy infants are born each year to women with hypothyroidism, hyperthyroidism, Hashimoto’s thyroiditis, Graves’ disease, thyroid cancer, and other forms of thyroid disease.

If you have a thyroid disorder and are attempting to conceive, work with your endocrinologist, obstetrician, and other physicians to develop a strategic treatment plan before you become pregnant. The earlier you begin monitoring your hormone levels during pregnancy, the better your chances of delivering a healthy infant with no birth defects or developmental problems. Be sure to check back each week for more of the thyroid health news you need.

For Further Reading

• http://thyroid.about.com/library/weekly/aa012502a.htm
• http://www.greenjournal.org/cgi/content/abstract/110/2/369