Preeclampsia Linked to Reduced Thyroid Function

Nov. 17, 2009 -- Pregnant women who develop
preeclampsia may have an increased risk for reduced thyroid function later in life,
new research indicates.
About 3% to 5% of women experience preeclampsia, characterized by high blood
pressure and protein in the urine that develops during the second half of
pregnancy and can be dangerous for the mother and fetus.
Researchers from the National Institutes of Health (NIH) and other
institutions report in the journal BMJ that women with preeclampsia may
be more likely to have slightly reduced thyroid function during the last weeks
of their pregnancies, but also decades later.
Preeclampsia and Hypothyroidism
Richard J. Levine, MD, MPH, a senior investigator in the Eunice Kennedy
Shriver National Institute of Child Health and Human Development, reports with
colleagues on an analysis combining two separate studies. Each suggests a link
between preeclampsia and reduced thyroid function.
The first shows that women who develop preeclampsia are more likely to have
slightly reduced thyroid function during the final weeks of their pregnancies.
The second study shows that women who develop preeclampsia are also more likely
to have reduced thyroid function more than 20 years after giving birth.
“The findings suggest that the possible development of hypothyroidism is a
consideration in patients with a history of preeclampsia,�? says Susan B.
Shurin, MD, acting director of the National Institute of Child Health and Human
Development. “Reduced thyroid functioning is easy to diagnose when suspected
and inexpensive to treat. Replacement therapy substantially improves quality of
life of affected persons.�?
The thyroid gland makes hormones that help regulate heart rate, blood pressure,
body temperature, and the conversion of food into energy. Hypothyroidism, or
reduced thyroid functioning, results in weakness, fatigue, and other
symptoms.
High TSH After Preeclampsia
Levine and collaborators from the Norwegian University of Science and
Technology, Harvard Medical School, and Howard Hughes Medical Institute tested
blood samples from an earlier study led by the NIH for levels of thyroid
stimulating hormone, or TSH, which stimulates the thyroid gland to make thyroid
hormones. TSH is typically elevated with hypothyroidism.
The U.S. study was based on thyroid function tests from 140 pregnant women
who had developed preeclampsia and 140 pregnant women who hadn’t.
Before the onset of preeclampsia, both groups of women had similar levels of
TSH and other thyroid function tests. After the onset of preeclampsia, women in
the preeclampsia group had higher levels of TSH than the women without
preeclampsia.
The researchers also examined data from Norway, where 7,121 women who’d
given birth to a first child in 1967 or later had had their blood sampled for
thyroid function in the mid-1990s.
The women who had preeclampsia in their first pregnancy were more likely to
have high TSH years later than the women without history of preeclampsia, the
researchers report. The scientists say the association was especially strong if
preeclampsia had occurred in two pregnancies.
Women with a  history of preeclampsia also have an increased risk of kidney disease, as well as high
blood pressure and other cardiovascular problems.
The rise in TSH levels was strongly associated with levels of a protein
called soluble fms-like tyrosine kinase 1, and the increase was greater in the
women with preeclampsia. The researchers write that this suggests that the
effect of preeclampsia on thyroid function may be mediated by this protein.
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