Hypothyroidism in pregnancy: what is the target of TSH during treatment? A case-control study

Abstract

Introduction: Hypothyroidism represents a frequent dysfunction in clinical practice, especially in women of reproductive age. During pregnancy, if not properly treated, it is related to an increased risk of adverse outcomes. Although treatment is indicated, doubts remain about what would be the best target level of thyroid-stimulating hormone (TSH) to be aimed. Purpose: To compare maternal and fetal outcomes in pregnant women with primary hypothyroidism, treated with levothyroxine, maintained with average TSH levels equal or lower than 2.5 mIU/L or between 2.6 and 4.0 mIU/L. Methods: Retrospective case-control study with pregnant patients diagnosed with primary hypothyroidism and on treatment with levothyroxine. Simple arithmetic averages will be calculated with 4 measurements of TSH and FT4 performed in different months after the 12th gestational week. The "case" group will include patients maintained with average TSH levels between 2.6 and 4.0 mIU/L, and the "control" group will consist of pregnant women with TSH levels below or equal to 2.5 mIU/L. Maternal-fetal outcomes will be compared in both groups of patients. Maternal-fetal outcomes will be compared in both groups of patients. Student's t-test or adjusted gamma linear model will be used to compare numerical variables and chi-square or Fisher's exact test for categorical variables. Logistic regression models will also be used to assess the risk factors for the outcomes, with the variables that present a significant difference in the initial analysis.