During pregnancy, which laboratory parameters should be monitored to manage hypothyroidism?

During pregnancy, which laboratory parameters should be monitored to manage hypothyroidism?

• A. Renin and aldosterone
• B. HbA1c
• C. TSH and free T4
• D. Calcium and PTH

Answer: (C)

During pregnancy, tracking thyroid status relies on both TSH and free T4. The pregnancy state changes thyroid physiology: estrogen raises thyroid-binding globulin, which increases total T4 and T3, but the free (unbound) hormone is what actually acts on tissues. Early in pregnancy, hCG can transiently stimulate the thyroid and suppress TSH, so TSH alone may not reliably reflect adequacy of thyroid hormone replacement. Measuring both TSH and free T4 provides a clearer picture of maternal euthyroidism and helps guide levothyroxine dose adjustments to protect both maternal health and fetal development. Renin and aldosterone relate to fluid and blood pressure regulation, not thyroid function monitoring. HbA1c tracks long-term glucose control, not thyroid status. Calcium and PTH pertain to calcium metabolism and parathyroid function, not the management of hypothyroidism during pregnancy.

During pregnancy, tracking thyroid status relies on both TSH and free T4. The pregnancy state changes thyroid physiology: estrogen raises thyroid-binding globulin, which increases total T4 and T3, but the free (unbound) hormone is what actually acts on tissues. Early in pregnancy, hCG can transiently stimulate the thyroid and suppress TSH, so TSH alone may not reliably reflect adequacy of thyroid hormone replacement. Measuring both TSH and free T4 provides a clearer picture of maternal euthyroidism and helps guide levothyroxine dose adjustments to protect both maternal health and fetal development.

Renin and aldosterone relate to fluid and blood pressure regulation, not thyroid function monitoring. HbA1c tracks long-term glucose control, not thyroid status. Calcium and PTH pertain to calcium metabolism and parathyroid function, not the management of hypothyroidism during pregnancy.