A 29-year-old woman presents with weight gain, fatigue, constipation, and a TSH of 7.8 mIU/L with free T4 of 0.7 ng/dL. Anti-TPO antibodies are 640 IU/mL. She is 10 weeks pregnant. What is the target TSH for the first trimester of pregnancy in this patient?

• A < 4.0 mIU/L
• B < 0.5 mIU/L
• C < 1.0 mIU/L
• D < 2.5 mIU/L ✓

Explanation

The American Thyroid Association 2017 guidelines recommend maintaining TSH < 2.5 mIU/L in the first trimester of pregnancy in women with hypothyroidism on levothyroxine. Untreated hypothyroidism in pregnancy carries risks of miscarriage, pre-eclampsia, and impaired fetal neurodevelopment. Trimester-specific upper reference limits apply; < 4.0 mIU/L applies to the second and third trimesters. Suppressed TSH < 0.5 would represent overtreatment.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.