by Mary
Shomon
June 2004 --
In announcements made in mid-May 2004 by the American Thyroid Association, the endocrinology community is now recommending guidelines regarding hypothyroidism and pregnancy that have been included in my book Living Well With Hypothyroidism since back in 2000, and in my recent Thyroid Guide to Fertility, Pregnancy and Breastfeeding Success.
There is no disagreement that a mother's thyroid function can have an impact on the outcome of a pregnancy and the development of her child. Endocrinologists have agreed for decades that overt hypothyroidism needs to be treated during pregnancy to prevent an adverse outcome for both mother and baby.
But the need for frequent testing during pregnancy, the likelihood of a need for increased thyroid hormone medication during pregnancy, and the risk of thyroid antibodies -- among other factors -- have been controversies and many physicians have refused to acknowledge these situations.
The American Thyroid Association (ATA) has, however, now come around to the position that there is a potential for an adverse outcome when a mother has subclinical hypothyroidism (where the T4 levels are normal, and TSH is slightly elevated) and when a mother has thyroid autoantibodies.
Bottom line? The ATA is now saying that even mild hypothyroidism can cause serious problems with the pregnancy, including premature birth or lower IQ in the baby.
This is a major departure, as until recently, many endocrinologists insisted that thyroid antibodies, or mild hypothyroidism had no impact on fertility, pregnancy, or the development of the baby.
According to the ATA Statement:
- Pregnant mothers with overt or subclinical hypothyroidism are at an increased risk for premature delivery.
- Pregnant mothers with detectable thyroid autoantibodies and normal thyroid function are at an increased risk for miscarriage and for postpartum thyroid disease including thyroiditis, hyperthyroidism (Graves' Disease) and also hypothyroidism.
- The offspring of mothers with thyroid hormone deficiency or thyroid stimulating hormone elevation during pregnancy may be at risk of mild impairment in their intellectual function and motor skills.
- Pregnant women being treated with thyroid hormone replacement often require a 30-50% increase in their thyroid hormone dose.
The ATA is calling for more extensive research into the nature of these problems, as well as the need for expanded testing programs.
In the meantime, the ATA is calling for testing before pregnancy and in early pregnancy of women who are at high risk for thyroid disease. Those at risk include those who have had previous thyroid problems, those with previous or existing autoimmune disease, and those with thyroid and autoimmune conditions in the family.
And, among those women who are already diagnosed with hypothyroidism, they need more frequent testing to ensure that they are not subclinically hypothyroid, and to ensure proper dosage.
What Should You Do?
While the ATA and endocrinologists debate what research is necessary in the bigger picture, women who are contemplating pregnancy have options:
Women who are contemplating pregnancy -- even those without a personal or family history of thyroid or autoimmune disease -- should , as a precautionary measure, get a basic TSH test. This can be done through your doctor, or you can purchase a home test kit.
Any woman who has a personal or family history of thyroid or autoimmune disease -- should have her thyroid tested prior to becoming pregnant, and again within the first weeks of early pregnancy. She should be tested throughout the pregnant as often as symptoms might indicate, but at least once a trimester.
Any woman with a diagnosed thyroid condition should have her thyroid tested prior to becoming pregnant, and again within the first several weeks of early pregnancy. She should be tested frequently throughout the pregnancy, including several times in the first trimester, and throughout the pregnancy as often as clinical signs and symptoms might indicate, but at least once in each of the second and third trimesters.
Women contemplating pregnancy should make sure they start taking a prenatal vitamin that includes not only folic acid, but iodine, before becoming pregnant, and continue taking that vitamin throughout pregnancy. (Note, however, that women taking a prenatal vitamin with iron will need to be careful about separating the vitamins from their thyroid hormone by at least 3-4 hours at minimum, or othe iron may make the thyroid hormone less effective by interfering with absorption.)
For information on getting pregnant, and having a safe, healthy pregnancy for both mother and baby, despite thyroid conditions, read the Thyroid Guide to Fertility, Pregnancy and Fertility Success.
Prenatal Thyroid Screening Proves Beneficial to Women and Their Children
Routine thyroid screening for women of reproductive age, particularly before they
become pregnant, may save money and limit health risks to children, according to new research being
presented this week at The Endocrine Society's 86th Annual Meeting in New Orleans. The new findings
provide a basis for quantifying costs and assessing effectiveness of different thyroid screening strategies
for reproductive age women.
Previous research has shown that low levels of thyroid hormone in pregnant women can cause mildly
impaired development in their children. As a result, some experts have advocated screening women of
childbearing age for thyroid disease.
In order to assess the potential cost and impact of screening, Dr. Ruth M. Belin and colleagues at the
John Hopkins University School of Medicine in Balitmore gathered data from 5, 516 women ages 17 to
45 from the Third National Health and Nutrition Examination Survey (NHANES III) performed by the
National Center for Health Statistics at the Centers for Disease Control and Prevention of American.
They found that low thyroid hormone levels affect an estimated 40,000 pregnant and 1.6 million nonpregnant women in the United States. They also concluded that, 3.1 percent of reproductive age women in the United States have low thyroid hormone levels.
"Previous studies have focused on the prevalence of low thyroid hormone levels in women who already
know they are pregnant, rather than the prevalence in women who do not realize they are pregnant or
could become pregnant. During the first 12 weeks of pregnancy, fetal brain development relies on
maternal thyroid hormone therefore a targeted screening of women before they become pregnant may
prove effective in preventing developmental problems," explained Dr. Belin.
Maternal Thyroid Disorder Linked to Learning Disabilities in Children: Endocrine Disrupting Chemicals May Be Involved; Routine Screening Urged for Women in Childbearing
Years
(Washington, DC) -- A recent study published in The New England Journal of Medicine found that some
learning disabilities in children may be the result of an untreated thyroid disorder their mothers
experienced during pregnancy. Other recent studies have found that maternal exposure to certain
chemicals, such as PCBs, may be exacerbating the problem by lowering maternal thyroid hormones,
which play an essential role in fetal brain development. Experts in the field and the Learning Disabilities
Association of America are calling for routine thyroid hormone screening for all women of childbearing
age and treatment when indicated.
Experts Debate Benefits and Costs of Thyroid Screening in Pregnancy
Thyroid problems at any time during a woman's pregnancy are associated with pregnancy-related complications and may be detrimental to the infant's neural development, said the American Thyroid Association (ATA) in a statement released recently. This information was echoed by other experts in thyroid diseases and fetal and women's health at a recent symposium sponsored by the the ATA and the American Association of Clinical Endocrinologists (AACE).
In addition, the ATA statement calls for prospective studies looking at population screening and treatment of asymptomatic – or subclinical – hypothyroidism, also known as an underactive thyroid. The organization of thyroid specialists also proposes public education initiatives, including messages about maternal thyroid health in over-the-counter pregnancy test kits.
The April 2, 2004 symposium in Alexandria, Va., titled The Impact of Maternal Thyroid Status on Pregnancy and Fetal and Childhood Development, brought together top researchers and clinicians in obstetrics and gynecology, neonatology, and thyroid diseases to explore important clinical and policy issues to educate caregivers about the best diagnosis, treatment, and monitoring strategies as well as public policy issues that influence how care is provided.
"Maternal hypothyroidism and autoimmune thyroid disease – like Hashimoto's thyroiditis, a type of hypothyroidism, or underactive thyroid – increase the risk of pregnancy complications, such as miscarriage, prematurity, gestational hypertension, and pre-eclampsia, as well as deficits of intellectual development in children," said Stephen H. LaFranchi, MD, of the Oregon Health & Science University in Portland, Ore., and a co-chair of the symposium. "The symposium tackled many unresolved issues, such as whether it is time to consider pilot screening programs of women for maternal hypothyroidism as a preventive measure, just as we screen newborns for congenital hypothyroidism to prevent the condition's harmful effects."
The experts described why maternal thyroid hormone is so important to the developing fetus. Gabriella Morreale de Escobar, MD, of the Instituto de Investigaciones Biomedicas, "Alberto Sols," in Madrid, Spain, explained that the fetus depends solely on the mother in the first half of gestation for thyroid hormone, especially thyroxine, needed for the developing brain. She added that pregnant women who are underproducing thyroxine are, therefore, at risk of having children with lower IQs and learning problems, such as attention-deficit hyperactivity disorder, whether or not their circulating thyroid-stimulating hormone (TSH) concentrations are increased. The most frequent cause of the inability of the maternal thyroid to produce enough thyroxine for fetal brain development is an inadequate supply of iodine. Amounts of this micronutrient, a necessary component of thyroid hormone, are needed with the onset of pregnancy and are almost double those needed by children and non-pregnant adults. "Intellectual impairments of many children could be easily prevented by promoting the use of iodine supplements taken before pregnancy throughout gestation and lactation," Dr. Morreale said.
The ATA statement concurs, emphasizing that pregnant and nursing women should take daily vitamin supplements that contain iodine, at least 220 micrograms a day for pregnant women and 290 micrograms daily for lactating women. Experts caution that only 35 percent of prenatal vitamins contain iodine. Worldwide, iodine deficiency remains the major factor responsible for intellectual impairment, although, in the United States, says the ATA statement, iodine nutrition is adequate. Even so, the statement goes further to say that new data indicate that some U.S. women of reproductive age may be at risk for slightly deficient intake. Furthermore, the ATA believes there is a need for research to clarify the iodine nutrition status of pregnant women in the United States, including measuring iodine levels in breast milk and correlating with maternal iodine nutrition and factors such as smoking.
The effect of environmental agents on thyroid function and iodine nutrition was another important topic discussed at the symposium. R. Thomas Zoeller, PhD, Professor of Biology at the University of Massachusetts in Amherst, said that ammonium perchlorate, a contaminant in some water supplies, is known to reduce the ability of the body to use existing iodine. Moreover, PCBs (polychlorinated biphenyls) are known to influence thyroid function and thyroid hormone action, which can alter iodine uptake during pregnancy and lactation. PCBs also appear to influence thyroid hormone action in tissues, including the developing brain. Thiocyanates in cigarette smoke are as a negative factor as well. "Chemicals in the environment can affect thyroid function in the mother and fetus and thyroid hormone 'signaling action' in the developing brain," concluded Dr. Zoeller.
Another potential problem related to hypothyroidism was described at the symposium by Daniel Glinoer, MD, PhD, who heads the Thyroid Investigation Clinic & Endocrine Section at the University Hospital Saint Pierre in Brussels, Belgium. "Five percent to 8 percent of women carry thyroid autoantibodies," he stated. These autoantibodies are strongly linked to the occurrence of miscarriage as well as a condition that occurs after delivery, called post-partum thyroiditis. Symptoms include depression, fatigue, and difficulty nursing. "Subclinical hypothyroidism – when the person has no visible symptoms and the condition is only detectable through labortary tests – is often undiagnosed, and the severity of hypothyroidism increases with gestational time." He estimated, "Five percent to 10 percent of the young female population could be affected, which has negative public health consequences." Dr. Glinoer also discussed hyperthyroidism – an overactive thyroid – explaining that it is "relatively uncommon in pregnancy but can be severe if untreated."
Kenneth J. Leveno, MD, Gillette Professor of Obstetrics and Gynecology at the University of Texas Southwestern Medical Center at Dallas and Chief of Obstetrics at Parkland Health and Hospital System, brought in the view of the obstetrician-gynecologist in stating that he does not believe that all women should be screened for thyroid dysfunction at this time because the current evidence is insufficient to warrant such universal screening. He added, "Given that the prevalence of subclinical hypothyroidism is about 2.5 percent in the United States and there are about 4 million births each year, appoximately 100,000 pregnant women would have to be treated. To do this is unjustified at this time."
The Medical Director of the March of Dimes, Nancy Green, MD, discussed the guidelines issued by the American College of Obstetricians and Gynecologists (ACOG) in 2002, which she noted were based primarily on consensus and expert opinion. ACOG stated at that time that there were insufficient data to warrant routine screening of asymptomatic pregnant women for hypothyroidism. ACOG recommended that testing of thyroid function may be performed in women with a personal history of thyroid disease or symptoms of thyroid disease.
The March of Dimes, said Dr. Green, appreciates the ATA's current review of the issue, which is in consideration of whether routine maternal thyroid screening and treatment – before conception and/or in early pregnancy – improves child cognitive development. The March of Dimes is focused on this issue primarily if it helps prevent pediatric harm. In addition, the March of Dimes is currently conducting a national campaign to prevent preterm birth, a side effect of maternal hypothyroidism.
Preterm birth, as Brian M. Casey, MD, Associate Professor of Obstetrics and Gynecology at the University of Texas Southwestern Medical Center at Dallas, pointed out, is the most common recognized cause of neuropsychological dysfunction in children. After reviewing the association of subclinical hypothyroidism with preterm birth, he concluded that "Prematurity may explain some of the neurodevelopmental abnormalities associated with maternal thyroid insufficiency."
The ATA statement emphasizes this research finding, stating that "pregnant mothers with overt or subclinical hypothyroidism are at an increased risk for premature delivery."
Other important research findings highlighted by the ATA statement include –
Pregnant mothers with detectable thyroid autoantibodies and normal thyroid function are at an increased risk for miscarriage and for postpartum thyroid disease,
Pregnant mothers with thyroid hormone deficiency or TSH elevation during pregnancy may have children at risk of mild impairment in their intellectual function and motor skills, and
Pregnant women being treated with thyroid hormone replacement often require a 30-percent to 50-percent increase in their thyroid hormone dose.
The ATA believes that the magnitude of these problems should be clarified, and programs should be developed to manage these health issues.
P. Reed Larsen, MD, a Professor of Medicine at Harvard Medical School and Chief of the Endocrinology Division at Brigham & Women's Hospital in Boston, asserted that there is not yet data that backs up the need for population-wide screening; however, he emphasized that the "threshold should be low for identifying at-risk women for screening. These factors include women who have a family or personal history of thyroid disease, goiter, diabetes, history of miscarriage, or symptoms suggesting hypothyroidism." The ATA also makes this assertion.
As for women who have known hypothyroidism before conception, Dr. Larsen strongly advised that physicians should provide pre-pregnancy counseling about the risks and changes in therapy that are needed. It is also important that these women have their thyroid hormone levels – TSH, in particular – checked as soon as pregnancy is confirmed. He and his colleagues have shown that many of these women will need to increase their thyroxine replacement as much as 50 percent in the first trimester.
"With these steps, as well as careful monitoring of TSH, we should be able to maintain normal thyroid hormone availability to the fetus during this critical period of development before fetal thyroid maturation occurs," added Dr. Larsen.
John H. Lazarus, MA, MD, Professor of Clinical Endocrinology at the University of Wales College of Medicine, Llandough Hospital in Cardiff, Wales, United Kingdom, added that there is substantial evidence from both retrospective and prospective studies suggesting that early gestational low maternal circulating thyroxine – a thyroid hormone, also known as T4 – concentrations adversely affect neonatal and child development at least to age 7.
Acknowledging the current lack of clinical trial data, he presented preliminary information about a current randomized, prospective study called CATS (Controlled Antenatal Thyroid Screening), which aims to ascertain if screening for thyroid function in early pregnancy is justified. The study plans to enroll 22,000 women when they are less than 16 weeks gestation and will look at whether treating thyroid disorders with thyroxine therapy during pregnancy can prevent adverse outcomes. Following delivery, the children will be tested with appropriate psychological evaluation at ages 2 and 5.
Paul Ladenson, MD, Director of the Division of Endocrinology and Metabolism at Johns Hopkins Medical School in Baltimore reviewed the benefits and costs of identifying pregnant women at risk of hypothyroidism. He concluded that "gestational hypothyroidism probably occurs with a significant incidence; TSH testing can diagnose the condition and thyroxine can treat it; and maternal and fetal consequences appear to be clinically significant based on anecdote and small clinical trials, and reversibility could be predicted." However, he added, "Evidence from definitive prospective, randomized clinical trials is lacking, and the cost of this new preventive medical intervention would be substantial."
"While most of the experts agreed that current scientific data falls short of supporting immediate widespread population screening for thyroid disease and thyroid autoimmunity," said Gregory Brent, MD, of the UCLA School of Medicine and the ATA Secretary, "there is sufficient information to recommend some interim measures and guidance for additional data that is required to design an effective screening program."
The ATA statement includes a "plan for action" that calls on governmental institutions, such as the Centers for Disease Control and Prevention; professionals organizations, such as the ATA and AACE; and nongovernmental groups, such as the March of Dimes, to implement a coordinated program of patient education, practice review, and research on the impact of maternal thyroid status on pregnancy and fetal and childhood development.
Reproductive-Age Women May Benefit From Thyroid Antibody Screening
According to researchers presenting study results at the June 2004
Endocrine Society annual meeting, pregnant women may benefit from
prenatal screening for thyroid antibodies known as anti-thyroperoxidase
(TPO), particularly when there is an elevated thyroid stimulating
hormone (TSH) level.
Ruth Belin, MD, from the Division of Endocrinology at John Hopkins
University School of Medicine in Baltimore, Maryland, told Medscape:
"Prior work has demonstrated that [children of] women who unwittingly
had abnormal thyroid [levels] during the time of pregnancy have had
adverse neuropsychological developments. Depending on the degree of
thyroid abnormality, neuropsychologic impairment could involve a very
subtle decrease in IQ scores.... Some studies have also looked at
visual changes and memory changes in children who are hypothyroid
or who have been exposed to hypothyroidism."
While studies have looked at women in the first trimester of pregnancy,
the researchers feel that screening women prior to pregnancy is important,
because they may be well into the first triemester before seeing an
obstetrician for screening.
Researchers used TSH test data from the Third National Health and
Nutrition Examination Survey (NHANES III), and concluded that as many
as 1.3% of pregnant women and 3.1% of all women who could potentially
become pregnant had TSH elevations higher than 4.5 mU/L. (And note
that according to more recent guidelines, endocrinologists now believe
that levels above 3.0 constitute hypothyroidism, so these percentages
would be higher.)
Since elevated TSH was seen far more often in women who had thyroid
antibodies, the researchers believe that prenatal antibody testing
may help identify women at risk -- and serve as a first step in screening.
Source: ENDO 2004: Abstract P2-473. Presented June 17, 2004.
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