Link Found Between Preeclampsia and Reduced Thyroid Function

A new study has found that women who experience preeclampsia, a serious complication of pregnancy, may have an increased risk for reduced thyroid functioning later in life.

Researchers from the U.S. National Institutes of Health (NIH; Bethesda, MD, USA), the National Institute of Child Health and Human Development (NICHD; Rockville, MD, USA), the Norwegian University of Science and Technology (NTNU; Trondheim), and other institutions analyzed data from two separate studies in which each suggest a link between preeclampsia and reduced thyroid function. In the first study, the Calcium for Preeclampsia Prevention trial of healthy pregnant nulliparous women held in the United States between 1992-1995, women who developed preeclampsia were more likely to have slightly reduced thyroid functioning during the last weeks of their pregnancies; the second study, the Norwegian Nord-Trondelag Health Study (HUNT-2), held between 1995-1997, found that women who had preeclampsia during their pregnancies were more likely to have reduced thyroid functioning more than 20 years after they had given birth, when compared to women who had not had preeclampsia during pregnancy.

The researchers tested blood samples collected in the studies for levels of thyroid stimulating hormone (TSH), which stimulates the thyroid gland, and found a link between preeclampsia and reduced thyroid functioning. The first study showed that early in their pregnancies, the women who went on to develop preeclampsia had thyroid functioning identical to that of the women who never developed preeclampsia. Toward the end of their pregnancies, the women with preeclampsia had, on average, much higher levels of TSH than women with no history of preeclampsia. However, the first study did not provide information on whether reduced thyroid functioning extended beyond the end of the pregnancy, when preeclampsia's symptoms ceased.

The researchers next turned to data collected in the mid-1990s in the Norway population study. The researchers analyzed data from 7,121 women who had given birth to a first child in 1967 or later, and had had their blood samples tested for thyroid function in the countywide study in the mid-1990s. The researchers discovered that the women who had preeclampsia in their first pregnancy were 1.7 times as likely to have high TSH as the women who had not had preeclampsia. Women who had preeclampsia in both their first and second pregnancies were nearly 6 times as likely to have high TSH levels. The study, which described the analysis of both studies, was published in the November 17, 2009, issue of BMJ (formerly known as the British Medical Journal).

"The findings suggest that the possible development of hypothyroidism is a consideration in patients with a history of preeclampsia,” said Susan Shurin, M.D., acting director of the NICHD. "Reduced thyroid functioning is easy to diagnose when suspected, and inexpensive to treat. Replacement therapy substantially improves quality of life of affected persons.”

Preeclampsia is a medical condition where hypertension arises in pregnancy in association with significant amounts of protein in the urine. Because preeclampsia refers to a set of symptoms rather than any causative factor, it is established that there are many different causes for the syndrome.

Related Links:
U.S. National Institutes of Health
U.S. National Institute of Child Health and Human Development
Norwegian University of Science and Technology