In hypothyroidism during pregnancy, which laboratory finding is typical?

• A. Elevated TSH
• B. Decreased TSH
• C. Normal TSH
• D. Elevated T4

Answer: (A)

Elevated TSH is most consistent with hypothyroidism during pregnancy because when the thyroid isn’t producing enough hormone (T4/T3), the pituitary rises TSH to stimulate the thyroid. This feedback loop means the typical pattern is a high TSH with low free T4, reflecting overt hypothyroidism. The other patterns don’t fit: elevated T4 would suggest hyperthyroidism, normal TSH would not explain the lack of thyroid hormone production, and a decreased TSH would point away from hypothyroidism. In pregnancy, this elevation still remains the hallmark finding guiding treatment with thyroid hormone replacement and close TSH monitoring.