Thyroid Disease in Pregnancy Kevin Trueblood Research Review

Overview What is known What questions are being asked What research is being done to answer these questions What does this research conclude about the topic Where can we go from here

What we know The thyroid is an essential endocrine gland that provides hormones for many key functions in our body. The thyroid is dependent on iodine to function properly. We know about the thyroid, we know about pregnancy, what we don’t know is how they correlate.

What questions are being asked (recent research) Thyroid disease in pregnancy is a hot topic for research right now because not much is known. Does hyperthyroidism in pregnancy increase the risk of birth defects (1-2)? Do certain thyroid diseases have more impact on pregnancy than others (3)? Does iodine supply influence the appearance of thyroid disease (4)?

Continued Can the hormones in the umbilical cord tell us what birth complications to expect (5)? Are pregnant women with thyroid disease at risk of heart disease (6)?

Hyperthyroidism and Birth Complications Kriplani A, Buckshee K, Bhargava VL, et al. Observed 12,260 women give birth in a New Delhi hospital over 7 years (1). 31 women were diagnosed with hyperthyroidism (0.261%). Those who were diagnosed before pregnancy had a 28% chance of birth complications Those diagnosed after had a 50% chance. Final conclusions: having hyperthyroidism drastically increases your chance of having birth complications.

Hyperthyroidism and Birth Complications Pillar N, Amalia L, Gershon H, and Eyal S. did a study that was almost identical to that of Kriplani’s (2). Differences: different location and different sample size. Of the 185,636 women, only 186 (0.1%) had hyperthyroidism. In direct conflict with previous study. Found a drastic increase in caesarian sections.

Disparities Between Diseases --Monsef F, Souheil O, Olfa M, et al. took a look at 3 specific thyroid disorders in pregnant women: TPO- ab, hypothyroidism, and hyperthyroidism (3). --They examined their blood work for thyroid-related hormones. --They found that 9.7% of women had TPO-ab, 6.5% had hypothyroidism, and 3.2% had hyperthyroidism --Correlations found with TPO-ab and hypothyroidism. Birth defects more common in TPO-ab and hypothyroidism.

Iodine Supply Fister P, Gaberscek S, Zaletel K, et al. set out to find whether or not an iodine rich diet had an impact on thyroid disease in pregnancy (4). A sample of 116 women from Slovenia was observed before and after each pregnancy for TSH and free thyroid hormones. These finding were compared with the UIC. Results: the UIC went up, and the hormones went down.

Cord Blood Hormones Yik-Si Chan L, Yu Chiu P, Kin Lau T took a sample of 24,892 women over a 4 year period and looked for correlations between THS levels in cord blood and various birth complications (5). preeclampsia, glucose intolerance, maternal medical diseases, and antepartum hemorrhage of unknown origin (APHUO)

Cord Blood Hormones Cord blood thyroid-stimulating hormone level is elevated in pregnancies complicated by preeclampsia, glucose intolerance, and maternal medical diseases. Further research is being done on whether these correlations are due to fetal hypoxia.

More In Depth Research Wilson K, Casey B, McIntire D, et al. have recently published a study comparing specific thyroid diseases with specific pregnancy issues (6). 24,883 women were observed to have mild preeclampsia, severe preeclampsia, or gestational hypertension. Researchers then observed how prevalent they were in each case of thyroid disease.

More In Depth Research Hyperthyroidism, hypothyroidism, and the euthyroid group as the control. The subclinical hyperthyroid group had a 6.2% chance of cardiovascular problems, the euthyroid group had an 8.5% chance, and the subclinical hypothyroid group had a 10.9% chance. After cross referencing all the data, scientists found a correlation between subclinical hypothyroidism and severe preeclampsia when compared to euthyroid women.

What Does this research conclude? Many conclusions have been drawn from this research, some conflicting with others. Whether or not hyperthyroidism is dangerous to pregnancy is still unknown. Consistent conclusions: Hypothyroidism is correlated with at least certain birth complications. TSH levels rise and fall in relation to the pregnancy complications. Thyroid disease, if left untreated, increases risk of birth complications.

Where Do We Go From Here? There is still so much unknown about the relationship between the thyroid and its impact on pregnancy. What I propose: We need to break this research down to its key components. These studies are too general to get the answers we need. We need to take each thyroid disease and compare it to each pregnancy complication individually so that we can find out WHY they are correlated. Only then can we hope to move towards curing diseases caused by the thyroid.

1. Kriplani A, Buckshee K, Bhargava VL, et al. Maternal and Perinatal Outcome in Thyrotoxicosis Complicating Pregnancy. European Journal of Obstetrics & Gynecology and Reproductive Biology Pg Pillar N, Amalia L, Gershon H, Eyal S. Pregnancy and Perinatal Outcome in Women With Hyperthyroidism. International Journal of Gynecology and Obstetrics Pg Monsef F, Souheil O, Olfa M, et al. Thyroid Disorders in Pregnancy: Frequency and Association with Selected Diseases and Obstetrical Complications in Tunisian Women Vol. 41/ Issue 12. Pg Fister P, Gaberscek S, Zaletel K, et al. Thyroid Function in the Third Trimester of Pregnancy and After Delivery in an Area of Adequate Iodine Intake. International Journal of Gynecology and Obstetrics Pg Yik-Si Chan L, Yu Chiu P, Kin Lau T. Cord Blood Thyroid-Stimulating Hormone Level in High-Risk Pregnancies. European Journal of Obstetrics & Gynecology and Reproductive Biology Pg Wilson K, Casey B, McIntire D, et al. Subclinical Thyroid Disease and the Incidence of Hypertension in Pregnancy. Obstetrics & Gynecology Vol. 119.

Questions?