Lacking population-level screening data from RCTs, most organizations do not recommend screening for thyroid dysfunction or they note insufficient evidence to make a screening recommendation (TABLE 217,19,20,34). In their most recent recommendation statement on the subject in 2015, the US Preventive Services Task Force (USPSTF) concluded the current evidence was insufficient to recommend for or against thyroid dysfunction screening in nonpregnant, asymptomatic adults.17 This differs from the ATA and the American Association of Clinical Endocrinology (AACE; formerly known as the American Association of Clinical Endocrinologists), which both recommend targeted screening for thyroid dysfunction based on symptoms or risk factors.20
What about subclinical hypothyroidism in pregnancy?
Overt hypothyroidism is associated with adverse events during pregnancy and with subsequent neurodevelopmental complications in children, although the effects of SCH during pregnancy remain less certain. Concerns have been raised over the potential association of SCH with pregnancy loss, placental abruption, premature rupture of membranes, and neonatal death.35 Historically, the prevalence of SCH during pregnancy has ranged from 2% to 2.5%, but using lower trimester-based TSH reference ranges, the prevalence of SCH in pregnancy may be as high as 15%.35
Guided by a large RCT that failed to find benefit (pregnancy outcomes, neurodevelopmental outcomes in children) following treatment of SCH in pregnancy,36 the American College of Obstetricians and Gynecologists (ACOG) recommends against routine screening for thyroid disease in pregnancy.34 The ATA notes insufficient evidence to rec-ommend universal screening for thyroid dysfunction in pregnancy but recommends targeted screening of those with risk factors.37 Data are conflicting on the benefit of treating known or recently detected SCH on pregnancy outcomes including pregnancy loss.35,38 As such, the American Society of Reproductive Medicine and the ATA both generally recommend treatment of SCH in pregnant patients, particularly when the TSH is ≥ 4.0 mIU/L and TPOAbs are present.37,39
a The ATA, ETA, and NICE have slightly different recommendations when a TSH level = 10 mIU/L. ETA and NICE recommend prioritizing treatment for individuals with this level, while ATA recommends treatment when individual factors are also considered.
ACKNOWLEDGEMENT The authors thank Family Medicine Medical Librarian Gwen Wilson, MLS, AHIP, for her assistance with literature searches.
CORRESPONDENCE Nicholas LeFevre, MD, Family and Community Medicine, University of Missouri–Columbia School of Medicine, One Hospital Drive, M224 Medical Science Building, Columbia, MO 65212; nlefevre@health.missouri.edu
