Additional Hormone Measurement Reveals High Risk Of Preeclampsia

An additional blood test for pregnant women accurately predicts which women with high thyroid function are at risk of developing preeclampsia. The findings may help identify high-risk pregnant women and potentially avoid unnecessary treatment that carries the risk of fetal abnormalities.

Preeclampsia is a condition that occurs during the second half of pregnancy, where women have high blood pressure and pass protein in their urine. It occurs in 2% to 8% of pregnancies and in some cases leads to serious complications for both mother and child, including seizures, kidney failure, hemorrhage and preterm birth.

Scientists at the Erasmus University Medical Center (Rotterdam, The Netherlands) measured the hormones of 5,153 women during early pregnancy, before the 18th week, and found that women with high levels of thyroid hormone but low levels of human chorionic gonadotropin (hCG) were between three and eleven times more likely to develop preeclampsia. One of the risk factors for preeclampsia is hyperthyroidism, which can be caused by medical conditions such as Graves’ disease or toxic thyroid nodules. However, high levels of hCG, a hormone that rises naturally during pregnancy, also leads to high thyroid function but this type of pregnancy-related hyperthyroidism does not have an increased risk of preeclampsia.

The combination of high-normal free thyroxine (FT4) levels with low hCG of less than 20, 000 IU/L) was associated with an 11.1-fold increased risk of preeclampsia. The combination of low thyroid-stimulating hormone (TSH) with low hCG of less than 0.000 IU/L was associated with an increased risk of preeclampsia ranging between a 9.2-fold increased risk for TSH of less than 0.1 mU/L, to an 8.7-fold increased risk for TSH <5th percentile and to an 3.8-fold increased risk for TSH of less than 0.4 mU/L. The combination of high-normal FT4 and hCG of more than 20,000 or low TSH and hCG of more than 20,000 was not associated with an increased risk of preeclampsia.

The authors concluded that the additional measurement of hCG in women with high normal thyroid function tests markedly improves the identification of women at high-risk of developing preeclampsia. This is likely to be due to the fact that hCG measurements allow for distinguishing physiologically high thyroid function caused by high hCG levels from pathophysiological high thyroid function due to autonomous production and/or TSH receptor stimulation antibodies.

Tim I M Korevaar, MD, the lead author of the study ,said, “Most pregnant women will have high thyroid hormone levels because of a natural rise in hCG, rather than an underlying thyroid condition like Grave's Disease or toxic nodules. Doctors do not currently screen for preeclampsia, although many do measure thyroid hormone during pregnancy. Measuring hCG as well may help doctors to more accurately interpret thyroid function tests in pregnant women.

Our work will potentially reassure the vast majority of patients who do not actually have an underlying thyroid condition by helping them avoid unnecessary treatment.” The study was presented at the 18th European Congress of Endocrinology held May 28 to May 31, 2016, in Munich, Germany.

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Erasmus University Medical Center