Intervalos de referencia de Tirotrofina y Tiroxina libre en población gestante

Abstract

INTRODUCTION: Thyroid hormones (TH) maintain the homeostasis of the body. Pregnancy involves important physiological changes in the maternal thyroid gland. During pregnancy, THs are essential in neuronal development, somatic growth and bone maturation of the fetus. Alterations in thyroid function produce adverse results in the pregnant woman, the fetus and the newborn (NB). TH values in pregnancy differ from the general population and change throughout pregnancy; therefore, for the correct evaluation of the thyroid axis, it is necessary to have appropriate reference intervals.

OBJECTIVES: Establish the reference intervals (RI) of thyrotrophin (TSH) and free thyroxine (FT4) in the pregnant population for each trimester of pregnancy and to know the prevalence of hypothyroidism.

MATERIALS AND METHODS: The serum concentrations of TSH and FT4 of pregnant women who attended for quarterly pregnancy check-ups were analyzed. Reference intervals were determined by direct method following the guidelines provided by the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) in Guide C28 A3 of the Clinical and Laboratory Standard Institute (CLSI).

RESULTS: It was found that it was not appropriate to partition the reference intervals for TSH by trimester of gestation. On the other hand, for FT4 a reference interval was obtained for the first trimester of gestation, and a different one for the second and third trimesters of gestation. A global prevalence of 1.8% of hypothyroidism in pregnancy was obtained.

CONCLUSION: The establishment of RI constitutes a contribution to the study of thyroid function in pregnancy, allowing early treatment to be installed and thereby reducing the implications of thyroid disease. It represents a practical tool designed to assist the doctor in making clinical decisions, thus ensuring the well-being of both the pregnant women and the fetus.