Abstract
The question of how to appropriately identify and treat hypothyroid women in pregnancy has been extremely controversial. The American Association of Clinical Endocrinologists has recommended routine TSH screening before pregnancy or during the first trimester in all pregnant women (9). The American College of Obstetricians and Gynecologists (ACOG) has recommended against serum TSH testing in asymptomatic pregnant women (10). Most recently, in its 2007 guidelines (endorsed by the American Thyroid Association, ATA) the Endocrine Society recommended aggressive case finding, but not screening, to detect hypothyroidism in pregnant women and noted that dose adjustment of L-T4 in women with preexisting hypothyroidism may be required by weeks 4–6 of pregnancy. However, case finding has its limitations; a recent report determined that even when risk factors are completely ascertained, 30% of pregnant women with hypothyroidism fail to be identified.
Most published guidelines related to the care of thyroid disorders, such as the recent ATA guidelines for the management of thyroid nodules and differentiated thyroid cancer (11), are written both by and for endocrinologists. However, the vast majority of hypothyroid women are not managed by endocrinologists during pregnancy, and the published subspecialty guidelines related to thyroid in pregnancy may not have reached the relevant audience. Previous survey data have suggested that providers' knowledge related to thyroid disease in pregnancy is suboptimal across all specialty groups, although endocrinologists scored higher than obstetricians, internists, and family practitioners (12).
In the current issue, Haymart examined practices of Wisconsin ACOG and American Academy of Family Physicians (AAFP) members related to the diagnosis and management of hypothyroidism in pregnancy (13). Only 11.5% of respondents reported having read the Endocrine Society guidelines. As expected, having read the Endocrine Society guidelines was associated with increased rates of prepregnancy counseling about L-T4 dose change requirements and with screening for thyroid disease risk factors in pregnant women.
Interestingly, although ACOG specifically recommends against universal thyroid screening, 15% of the Wisconsin respondents reported obtaining serum TSH values in all pregnant patients. Further, 36% of respondents routinely asked asymptomatic patients about the presence of thyroid disease risk factors (50% asked about the presence of risk factors in the presence of symptoms suggestive of hyper- or hypothyroidism). In essence, 51% of the physicians in the study either performed universal screening or attempted to identify high-risk patients. Perhaps the presence of the Endocrine Society guidelines has created a buzz in the medical community so that testing for thyroid dysfunction during pregnancy is now fashionable (similar to the seemingly universal screening for Vitamin D levels). We also do not know which way the curve is trending; that is, is there an ever-increasing number of providers who screen? Although our sense is that this may be occurring, re-surveying the physicians in Wisconsin in a few years would provide intriguing data.
The opinions and practices of thyroid subspecialists may be quite different from those of the Wisconsin survey respondents, with endocrinologists more likely to screen for thyroid function abnormalities in pregnant women. Attendees at the 2009 ATA Spring Symposium on Thyroid Dysfunction in Pregnancy were primarily endocrinologists (77%), but also included obstetricians (8%), reproductive endocrinologist (3%), internists (2%), pediatricians (2%), and others (8%). When an audience response system was used before a debate about the merits of thyroid screening in pregnancy, 76% were in favor of universal thyroid screening for pregnant women, 14% were opposed to universal screening, and 10% were undecided. When asked at the beginning of the symposium what testing they would order for an asymptomatic first-trimester pregnant woman with a family history but no personal history of thyroid disease, 98% of the 64 respondents reported that they would order serum TSH and/or thyroperoxidase (TPO) antibody levels. (Permission to collect and use these data was obtained from the pertinent Institutional Review Boards.)
In the Haymart study, practices regarding L-T4 dose adjustment in pregnancy were variable: 19% reported addressing doses at the time of positive home pregnancy test, 70% addressed doses at the time of the first prenatal visit, 2% at 7–9 weeks, and 8% at 10–12 weeks. Since the first prenatal visit in most centers typically does not occur until at least 8 weeks of gestation, these data suggest that L-T4 dose adjustments are not being addressed in a timely fashion for most patients. It is unclear whether this is primarily due to knowledge deficits or to logistical barriers.
Strengths of the Haymart study include a reasonable 52.5% response rate and demographic data suggesting that respondents were representative of Wisconsin ACOG and AAFP members. However, there is likely significant regional variation in practices (14) and survey respondents may not be representative of a national sample. In addition, prepregnancy counseling about the necessity for L-T4 dose changes in early pregnancy is more likely to be performed by primary care providers rather than obstetricians, given the usual timing of the initial prenatal visit.
It is anticipated that the results of ongoing and recently completed prospective studies will clarify the field and inform guidelines and behavior in the near future. Results of the Controlled Antenatal Thyroid Screening Study, carried out in the United Kingdom and Italy, are scheduled to be presented at the International Thyroid Congress in Paris in September 2010. The National Institutes of Health is currently carrying out a randomized multicenter trial of T4 therapy for subclinical hypothyroidism or hypothyroxinemia diagnosed during pregnancy; results of this trial will likely be reported in 2015. Data from an abstract presented at the 2009 ATA meetings demonstrating that treatment of subclinical thyroid disease during pregnancy decreases complications are currently in press. Finally, a recent study comparing current guidelines to universal screening for subclinical hypothyroidism in pregnancy demonstrated that universal screening was more cost effective under a wide range of circumstances (15).
The ATA has recently convened a new task force to create updated thyroid in pregnancy guidelines. Among the members of this task force are representatives from ACOG, the Society for Maternal–Fetal Medicine, and the Midwives Alliance of North America. It is hoped that the inclusion of representatives from all of these associations will be of help not just for formulating the guidelines but for their ultimate dissemination to relevant practitioners as well.