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Author: Admin | 2025-04-28
Delay the absorption of levothyroxine and reduce its bioavailability.7.10 Drug-Laboratory Test InteractionsConsider changes in TBG concentration when interpreting T4 and T3 values. Measure and evaluate unbound (free) hormone and/or determine the free T4 index (FT4I) in this circumstance. Pregnancy, infectious hepatitis, estrogens, estrogen-containing oral contraceptives, and acute intermittent porphyria increase TBG concentrations. Nephrosis, severe hypoproteinemia, severe liver disease, acromegaly, androgens, and corticosteroids decrease TBG concentration. Familial hyper- or hypo-thyroxine-binding globulinemias have been described, with the incidence of TBG deficiency approximating 1 in 9000.8 USE IN SPECIFIC POPULATIONS8.1 PregnancyRisk SummaryExperience with levothyroxine use in pregnant women, including data from post-marketing studies, have not reported increased rates of major birth defects or miscarriages (see Data). There are risks to the mother and fetus associated with untreated hypothyroidism in pregnancy. Since thyroid-stimulating hormone (TSH) levels may increase during pregnancy, TSH should be monitored and LEVOXYL dosage adjusted during pregnancy (see Clinical Considerations). There are no animal studies conducted with levothyroxine during pregnancy. LEVOXYL should not be discontinued during pregnancy and hypothyroidism diagnosed during pregnancy should be promptly treated.The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2 to 4% and 15 to 20%, respectively.Clinical ConsiderationsDisease-Associated Maternal and/or Embryo/Fetal RiskMaternal hypothyroidism during pregnancy is associated with a higher rate of complications, including spontaneous abortion, gestational hypertension, pre-eclampsia, stillbirth, and premature delivery. Untreated maternal hypothyroidism may have an
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