Levothyroxine therapy in pregnancy: Are we overtreating patients?

Background : Pregnancy imposes unique physiological requirements on the mother’s thyroid gland to meet the thyroid hormone demands both for her and the fetus. A lack of consensus in current guidelines on diagnosing thyroid dysfunction during pregnancy and administering levothyroxine raises concerns regarding treatment efficacy. As hypothyroidism—subclinical or overt—is a recognized risk factor for an unfavorable pregnancy outcome, the administration of excessive or unneeded therapy can also lead to complications. Objective : This study aims to evaluate the prevalence of levothyroxine replacement therapy among euthyroid pregnant women. Materials and methods : A retrospective cohort study was conducted using the data from 6237 pregnant women who delivered at the OB/GYN Hospital “Dr. Shterev” in Sofia, Bulgaria, between January 2017 and December 2022. Thyroid function data were available for 1746 pregnant women meeting inclusion criteria: aged > 18 years, with singleton pregnancies, and thyroid hormone level tests conducted no later than mid-second trimester. Results : According to pregnancy-specific thyroid disorder diagnostic criteria, patients were categorized into euthyroid (n = 1066), subclinical hypothyroidism (n = 421), overt hypothyroidism (n = 48), isolated maternal hypothyroxinemia (n = 160), gestational thyrotoxicosis (n = 46), and Graves’ disease (n = 5). Analysis revealed that 37.7% (n = 401) of euthyroid pregnant women were prescribed levothyroxine. Only 22.9% (n = 92) of euthyroid women received hormone replacement therapy due to autoimmune thyroiditis. Conclusion : Our findings prompt consideration regarding the appropriateness of levothyroxine therapy for euthyroid pregnant women. Clear guidance is warranted on the initiation of hormone replacement therapy during pregnancy.