Thyroid Disorders during Pregnancy and Puerperal Periods: A Narrative Review.

OBJECTIVES: Thyroid disorders are among the most clinically relevant endocrine conditions during pregnancy and the puerperal period. Given their clinical importance, this article aims to contextualize the role of thyroid dysfunction, particularly subclinical hypothyroidism, during these periods and to analyze the ongoing debate regarding screening and treatment based on international guideline recommendations. METHODS: This narrative literature review was conducted using the SciELO, PubMed/MEDLINE, Embase, UpToDate, and Virtual Health Library databases. In addition, official documents from the Brazilian Ministry of Health, the Brazilian Society of Endocrinology and Metabolism, the Brazilian Federation of Gynecology and Obstetrics Associations, the American Thyroid Association, the European Thyroid Association, the American College of Obstetricians and Gynecologists, and the Brazilian Association of Medical Education were reviewed. RESULTS: Thyroid disorders during pregnancy pose a clinical challenge due to physiological gestational changes, variability in thyroid-stimulating hormone and thyroxine reference ranges, and the influence of thyroid autoimmunity. Diagnostic definition is hindered by the lack of uniform laboratory reference intervals, contributing to overdiagnosis and unnecessary treatment. Evidence indicates that the benefit of levothyroxine therapy is mainly observed when the maternal thyroid-stimulating hormone level exceeds 4.0 mU/L and treatment is initiated early in pregnancy. In the postpartum period, the risk of persistent thyroid dysfunction highlights the importance of hormonal reassessment and individualized, evidence-based decision-making that accounts for population-specific factors. CONCLUSION: There is no clear consensus in the literature regarding the diagnosis and management of thyroid disorders during the pregnancy-puerperal cycle. Therefore, screening and care strategies should be expanded and adapted to local contexts in order to optimize maternal and fetal outcomes, while respecting regional epidemiological and laboratory characteristics.