Wang (201n1)a China 0.3% Cleary-Goldman (2008)a United States 0.3% Vaidya (2007)d United Kingdom 1.0% Casey (200S)b United States 0.2% Andersen (2016)d Denmark 1.2% has been reported to complicate between 2 and 12 per 1000 aScreened during first trimester.
pregnancies. It is characterized by insidious nonspeciic clini bScreened before 20 weeks.
cal indings that include fatigue, constipation, cold intolerance, (Includes those treated before pregnancy.
muscle cramps, and weight gain. A pathologically enlarged thy dDiagnosed in early versus later pregnancy.
roid gland depends on the etiology of hypothyroidism and is hypothyroidism, discussed later, is defined by an elevated serum TSH level and normal serum thyroxine concentration Qameson, 2015). Sometimes included in the spectrum of subclinical thyroid disease are asymptomatic individuals with high levels of anti-TPO or anti thyroglobulin antibodies. Autoimmune euthyroid disease represents a new investigative frontier in screening and treatment of thyroid dysfunction during pregnancy.
he most common cause of hypothyroidism in pregnancy is Hashimoto thyroiditis, characterized by glandular destruction from autoantibodies, particularly anti-TPO antibodies. Another cause is postablative Graves disease. Clinical identiication of hypothyroidism is especially diicult during pregnancy because many of the signs or symptoms are also common to pregnancy itself. Thyroid analyte testing should be performed on symptomatic women or those with a history of thyroid disease (American College of Obstetricians and Gynecologists, 2017). Severe hypothyroidism during pregnancy is uncommon, probably because it is often associated with infertility and higher spontaneous abortion rates (De Groot, 2012). Even women with treated hypothyroidism undergoing in vitro fertilization have a significantly lower chance of achieving pregnancy (Scoccia,r2012).
Treatment. The American hyroid Association and American Association of Clinical Endocrinologists (2011) recommend replacement therapy for overt hypothyroidism beginning with levothyroxine in doses of 1 to 2 ILg/kgl d or approximately 100 Lg daily. Women who are athyreotic after thyroidectomy or radioiodine therapy may require higher doses. Surveillance is with TSH levels measured at 4-to 6-week intervals, and the thyroxine dose is adjusted by 25-to 50-lLg increments until TSH values become normal. Pregnancy is associated with an increased thyroxine requirement in approximately a third of supplemented women (Abalovich, 2010; Alexander, 2004). The increased demand in pregnancy is believed to be related to augmented estrogen production (Arafah, 2001).
Greater thyroxine requirements begin as early as 5 weeks' gestation. In a randomized trial that provided an increased levothyroxine dose at pregnancy confirmation in 60 mothers, Yassa and coworkers (2010) found that a 29-to 43-percent increase in the weekly dose maintained serum TSH values <5.0 mUlL during the first trimester in all women. Importantly, however, this increase caused TSH suppression in more than a third of women. Significant hypothyroidism may develop early in women without thyroid reserve, such as those with a previous thyroidectomy, those with prior radioiodine ablation, or those undergoing assisted reproductive techniques (Alexander, 2004; Loh, 2009). Anticipatory 25-percent increases in thyroxine replacement at pregnancy conirmation will reduce this likelihood. All other women with hypothyroidism should instead undergo TSH testing at initiation of prenatal care.