A 30-year-old pregnant woman (20 weeks) is found to have subclinical hypothyroidism (TSH 5.8 mIU/L, free T4 normal, TPO antibodies positive). According to current ATA 2017 guidelines, the appropriate management is:

• A No treatment; recheck TSH at 24 weeks
• B Levothyroxine to maintain TSH 2.5–4.0 mIU/L
• C Carbimazole to suppress TSH
• D Levothyroxine to maintain TSH < 2.5 mIU/L ✓

Explanation

ATA 2017 guidelines recommend levothyroxine treatment for pregnant women with subclinical hypothyroidism if TSH > upper limit of trimester-specific reference range AND TPO antibodies are positive (or TSH > 10 mIU/L regardless of antibodies). With TPO-Ab positive and TSH 5.8 mIU/L at 20 weeks, treatment is indicated. The target TSH during pregnancy is < 2.5 mIU/L in the first trimester and < 3.0 mIU/L in the second and third trimesters. Carbimazole is used for hyperthyroidism, not hypothyroidism.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

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Written and medically reviewed by the StethoPrep medical team.