Niveles de tirotrofina y anticuerpos antitiroperoxidasa en el primer trimestre de gestación asociados a complicaciones del embarazo en la mujer eutiroidea

Abstract

Introduction

Pregnancy is a physiological state presenting with endocrine and immunological changes. The thyroid gland modifies its output in order to provide enough hormones to the mother and foetus. Thyroid autoimmunity and thyroid dysfunction are prevalent in women of childbearing age and may affect the course of gestation and having maternal and foetal clinical consequences. The purpose of the present study was to establish the relationship between euthyroid pregnant women with thyrotropin (TSH) at two levels of the reference range (< 1.2 and between 1.2 and 2.5 mIU/L), and positive or negative anti-thyroid peroxidase autoantibodies (TPO Ab) with the frequency of pregnancy complications and the development of thyroid dysfunction.

Methods

A retrospective study of euthyroid women in their first trimester of pregnancy was performed. TSH, free thyroxine (FT4), total thyroxine (T4), and TPOAb values were analysed. A total of 580 women had positive TPOAb (EP group), and 533 women had negative TPOAb (EN group). The EP and EN groups were subdivided according to TSH levels into EP1: positive TPOAb and TSH < 1.2, and EP2: positive TPOAb and TSH between 1.2 and 2.5 mIU/L. Maternal and foetal complications, such as miscarriage, intrauterine death, preterm delivery, and thyroid dysfunction during pregnancy and postpartum were taken into account.

Results

TSH values were higher in EP group vs EN group ($\overline{\text{X}}\pm \text{SD}$; 1.57 ± 0.82 vs 1.16 ± 0.54 mIU/L, P=.01). FT4 and T4 values were similar in both groups. Out of the pregnant women in the EP group, 63% were included in EP1, and 37% in EP2. In the EN group, 80% of women were included in EN1 and 20% in EN2. A significant (P=.001) increase in pregnancy complications in EP group (22%) vs EN (10%) was observed. In the EP group, TSH levels were: 1.65 ± 0.67 vs 0.99± 0.77 ($\overline{\text{X}}\pm \text{SD}$) mIU/L (P=.014) respectively, in women with and without miscarriage. TSH levels were 1.63 ± 0.70 vs 1.15 ± 0.53 ($\overline{\text{X}}\pm \text{SD}$) mIU/L (P=.012), respectively, in women with and without preterm delivery. In the EN group TSH levels were: 1.45 ± 0.61 vs 0.85± 0.66 ($\overline{\text{X}}\pm \text{SD}$) mIU/L (P=.001), respectively, in women with and without miscarriage. TSH levels were 1.59 ± 0.71 vs 0.83 ± 0.64 ($\overline{\text{X}}\pm \text{SD}$) mIU/L (P=.001), respectively, in women with and without preterm delivery. However, TSH levels in miscarriage and preterm delivery were similar. Thirty-two EP, and 19 EN women developed hypothyroidism in pregnancy (ns), and 29 EP and 10 EN women developed post-partum thyroiditis (P=.005).

Conclusion

Thyroid autoimmunity and higher TSH levels within the reference range during the first trimester of pregnancy were associated with pregnancy complications and with the development of thyroid postpartum dysfunction.