What medication adjustments should be made in the management of hypothyroidism in pregnant and lactating women, and how often should serum TSH levels be measured?

Updated: Mar 03, 2021
  • Author: Philip R Orlander, MD, FACP; Chief Editor: George T Griffing, MD  more...
  • Print

Increased thyroid hormone dosage requirements should be anticipated during pregnancy, especially in the first and second trimesters. Studies have suggested that in pregnant women with hypothyroidism, the LT4 dose should be increased by 30% at the confirmation of pregnancy and subsequently adjusted in accordance with TSH levels.

In addition, iodine demands are higher with pregnancy and lactation. Iodine needs rise from approximately 150 µg/day in the nonpregnant woman to 240-290 µg/day with pregnancy and lactation. Guidelines from the American Thyroid Association recommend that all pregnant and lactating women ingest a minimum of 250 mg iodine daily—optimally, in the form of potassium iodide, to ensure consistent delivery. [51]

For pregnant women with previously diagnosed hypothyroidism, serum TSH levels should be measured every 3-4 weeks during the first half of pregnancy and every 6-10 weeks thereafter. The LT4 dose should be adjusted so as to keep the serum TSH below 2.5 mIU/L. TSH and free T4 levels should be measured 3-4 weeks after every dosage adjustment. [52]

Did this answer your question?
Additional feedback? (Optional)
Thank you for your feedback!