Transient biochemical features of hyperthyroidism may be observed in 2 to 15 percent of women in early pregnancy (Fitzpatrick, 2010). Many women with hyperemesis gravidarum have abnormally high serum thyroxine levels and low TSH levels (Chap. 54, p. 1045). his results from TSH-receptor stimulation from massive-but normal for pregnancyconcentrations of hCG. This transient condition is also termed gestational transient thyrotoxicosis. Even if associated with hyperemesis, antithyroid drugs are not warranted (American College of Obstetricians and Gynecologists, 2017). The degree of hCG level elevation does not correlate with thyroxine and TSH values, which become more normal by midpregnancy (Nathan, 2014; Yoshihara, 2015).
he prevalence of increased thyroxine levels in women with a molar pregnancy ranges between 25 and 65 percent (Hershman, 2004). As discussed, abnormally high hCG levels lead to overstimulation of the TSH receptor. Because these tumors are now usually diagnosed early, clinically apparent hyperthyroidism has become less common. With molar evacuation, serum free T4 levels usually normalize rapidly in parallel with declining hCG concentrations. This is discussed further in Chapter 20 (p. 391).
hird-generation TSH assays with an analytical sensitivity of 0.002 mU/mL permit identiication of subclinical thyroid disorders. These biochemically defined extremes usually represent normal biological variations but may herald the earliest stages of thyroid dysfunction. Subclinical hyperthyroidism is characterized by an abnormally low serum TSH concentration in concert with normal thyroxine hormone levels (Surks, 2004). Long-term efects of persistent subclinical thyrotoxicosis include osteoporosis, cardiovascular morbidity, and progression
After 1-2 hours of thionamide therapy start iodine: if iodine anaphylaxis history, Lithium carbonate 300 mg PO every 6 hr
Consider corticosteroid therapy for 24 hours:
FIGURE 58-4 One management method for thyroid storm or thyrotoxic heart failure. gtt = drops; IV = intravenous; NGT = nasogastric tube; PO = orally; PTU = propylthiouracil.
to overt thyrotoxicosis or thyroid failure. Casey and Leveno (2006) reported that subclinical hyperthyroidism was found in 1.7 percent of pregnant women. Importantly, subclinical hyperthyroidism was not associated with adverse pregnancy outcomes. In separate retrospective analyses of almost 25,000 women who underwent thyroid screening throughout pregnancy, Wilson and colleagues (2012) and Tudela and coworkers (2012) also found no relationship between subclinical hyperthyroidism and preeclampsia or gestational diabetes.
Treatment of subclinical hyperthyroidism is unwarranted in pregnancy because antithyroid drugs may afect the fetus. hese women may beneit from periodic surveillance, and approximately half eventually have normal TSH concentrations.
Overt or symptomatic hypothyroidism, as shown in Table 58-3, more likely in women in areas of endemic iodine deiciency or those with Hashimoto thyroiditis. Other indings include edema, dry skin, hair loss, and prolonged relaxation phase of deep tendon relexes. Clinical or overt hypothyroidism is conirmed when an abnormally high serum TSH level is accompanied by an abnormally low thyroxine level. Subclinical
TABLE 58-3. Frequency of Overt Hypothyroidism