Testing, Monitoring, and Treatment of Thyroid Dysfunction in Pregnancy

J Clin Endocrinol Metab. 2021 Mar 8;106(3):883-892. doi: 10.1210/clinem/dgaa945.


Both hyperthyroidism and hypothyroidism can have adverse effects in pregnancy. The most common causes of thyrotoxicosis in pregnancy are gestational transient thyrotoxicosis and Graves' disease. It is important to distinguish between these entities as treatment options differ. Women of reproductive age who are diagnosed with Graves' disease should be counseled regarding the impact of treatment options on a potential pregnancy. Although the absolute risk is small, antithyroid medications can have teratogenic effects. Propylthiouracil appears to have less severe teratogenicity compared to methimazole and is therefore favored during the first trimester if a medication is needed. Women should be advised to delay pregnancy for at least 6 months following radioactive iodine to minimize potential adverse effects from radiation and ensure normal thyroid hormone levels prior to conception. As thyroid hormone is critical for normal fetal development, hypothyroidism is associated with adverse obstetric and child neurodevelopmental outcomes. Women with overt hypothyroidism should be treated with levothyroxine (LT4) to a thyrotropin (thyroid-stimulating hormone; TSH) goal of <2.5 mIU/L. There is mounting evidence for associations of maternal hypothyroxinemia and subclinical hypothyroidism with pregnancy loss, preterm labor, and lower scores on child cognitive assessment. Although there is minimal risk of LT4 treatment to keep TSH within the pregnancy-specific reference range, treatment of mild maternal thyroid hypofunction remains controversial, given the lack of clinical trials showing improved outcomes with LT4 treatment.

Keywords: maternal thyroid function; pregnancy; thyroid in pregnancy.

Publication types

  • Case Reports
  • Research Support, N.I.H., Extramural
  • Review

MeSH terms

  • Adult
  • Embryo Loss / etiology
  • Female
  • Graves Disease / complications
  • Graves Disease / diagnosis
  • Graves Disease / therapy
  • Humans
  • Infant, Newborn
  • Maternal Serum Screening Tests / methods
  • Maternal Serum Screening Tests / standards
  • Monitoring, Physiologic / methods
  • Pregnancy
  • Pregnancy Complications* / diagnosis
  • Pregnancy Complications* / therapy
  • Prenatal Care / methods
  • Tachycardia / diagnosis
  • Tachycardia / etiology
  • Tachycardia / therapy
  • Thyroid Diseases / complications
  • Thyroid Diseases / diagnosis*
  • Thyroid Diseases / therapy*
  • Thyroid Function Tests / methods
  • Thyroid Function Tests / standards
  • Thyrotoxicosis / complications
  • Thyrotoxicosis / diagnosis
  • Thyrotoxicosis / therapy
  • Weight Loss / physiology