Strict control of HYPOthyroidism during pregnancy

As soon as pregnancy is confirmed, recommend increasing the levothyroxine dose by 25% to 30%. One way to do this is to have the woman....
Mahitab Hany, BS Pharm, PGDipClinPharm, PGDipClinNutrition, BCNSP

As a clinical pharmacist, you should know how to treat hypothyroidism in pregnant women. New guidelines will call for tighter and more aggressive control of hypothyroidism before and during pregnancy. Levothyroxine needs rapidly increase when a woman becomes pregnant, leaving many patients undertreated during early pregnancy.

Hypothyroidism during pregnancy increases the risk of miscarriage, preterm birth, low birth weight, and cognitive deficits. Treatment should begin BEFORE a woman becomes pregnant. Recommend titrating levothyroxine doses to achieve a TSH less than 2.5 mIU/L when a woman is planning to become pregnant.

  • As soon as pregnancy is confirmed, recommend increasing the levothyroxine dose by 25% to 30%. One way to do this is to have the woman take an extra dose of levothyroxine two days per week as soon as she misses a period or has a positive home pregnancy test.
  • Recommend monitoring TSH every 4 weeks during the first half of pregnancy, and then at least once between 26 and 32 weeks of gestation.
    • Recommend aiming for a TSH of 2.5 mIU/L or less in the first trimester, and 3.0 mIU/L or less during the second and third trimesters.
  • After delivery, recommend returning to the woman's pre-pregnancy levothyroxine dose, and checking TSH in 6 weeks.
  • Remind women not to take levothyroxine and prenatal vitamins at the same time due to decreased levothyroxine absorption.
  • Recommend taking levothyroxine first thing in the morning on an empty stomach, and the prenatal vitamin at least 4 hours later with lunch or dinner. Get our note, "Monitor THYROID disease during pregnancy".

References

  1. Stagnaro-Green A, Abalovich M, et al. Guidelines of the American Thyroid Association for the diagnosis and management of thyroid disease during pregnancy and postpartum. Thyroid. 2011 Oct;21(10):1081-125.
  2. Abalovich M, Amino N, et al. Management of thyroid dysfunction during pregnancy and postpartum: an Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2007 Aug;92(8 Suppl):S1-47.
  3. Soldin OP, Soldin D, Sastoque M. Gestation-specific thyroxine and thyroid stimulating hormone levels in the United States and worldwide. Ther Drug Monit. 2007 Oct;29(5):553-9.
Mahitab Hany, BS Pharm, PGDipClinPharm, PGDipClinNutrition, BCNSP