Further understanding of thyroid function in pregnant women

ABSTRACT

Introduction

Normal thyroid status throughout pregnancy is important for both maternal and fetal health. Despite the bulk of contemporary research honing on thyroid function in gestation and the relevant disorders, there are still gaps in our current knowledge about the etiology and treatment of thyroid diseases in pregnant women.

Areas covered

This article analyzes the adaptation of the thyroid gland to gestational physiological changes and attempts to explain the effect of several factors on thyroid function in pregnancy. It also stresses proper utilization and interpretation of thyroid tests during pregnancy and underlines the significance of proper screening and treatment of pregnant women aiming at favorable health outcomes.

Expert opinion

Appropriate strategies for diagnosing and treating thyroid disease in pregnancy are important. Laboratory thyroid testing plays a leading role, but test results should be interpreted with caution. Given the possible serious maternal and fetal/neonatal complications of thyroid disease in pregnancy, we recommend universal screening with TSH measurements of all pregnant women. Additional assessment with determination of the levels of free thyroid hormones and thyroid antibodies may be necessary under certain conditions. The economic burden of such interventions should be considered.

KEYWORDS:

• Pregnancy
• thyroid diseases
• thyroid function tests
• thyroid gland
• thyroid hormones

Article highlights

• Interest in thyroid dysfunction during pregnancy has greatly intensified over the years mainly because of the potential serious complications in maternal and fetal/neonatal health.

• Several gestational physiological changes, including higher concentrations of thyroxine-binding globulin, elevated urinary iodine clearance, and increased thyroxine degradation by placental type III deiodinase, necessitate significant adaptations of thyroid function to ensure adequate supply of thyroid hormone to the mother and fetus.

• Serum TSH and free thyroid hormone reference ranges change throughout pregnancy and trimester-specific normal values should be available for the interpretation of thyroid testing results.

• The identification of risk factors, such as pre-existing thyroid disease, thyroid autoimmunity, iodine deficiency, use of thyroid-affecting medications, multi-parity, and in vitro fertilization, is important for improving the diagnostic sensitivity of thyroid disease among pregnant women.

• Extensive laboratory testing of pregnant women, by performing thyroid function tests and measuring thyroid antibodies, is an important strategy to reduce the adverse consequences of thyroid dysfunction, but it also burdens the cost of care.

Declaration of interest

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Reviewer disclosures

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Additional information

Funding

This paper was not funded.