Estudo longitudinal do eixo hipófise-tireóide durante a gravidez

Abstract

The thyroid undergoes important changes during pregnancy. In order to evaluate changes of the hypophyseal-thyroid axis during this period we studied the thyroid function in 587 pregnants by determining serum TSH, free T4, TPO antibodies and betahCG in the 1st trimester and serum TSH, free T4 and TPOAb in to 2nd and 3rd. We observed a progressive rise in average serum TSH in the 2nd (2.14 mU/L) and 3rd (2.96 mU/L) trimesters when compared to the 1st (1.39 mU/L). Serum TSH values in the 1st trimester were inversely correlated with betahCG levels in as much as TSH levels below 0.4 mU/L corresponded to average betahCG levels of 129,000 UI/L whereas these were 34,200 UI/L in the normal TSH group. A slight decrease in free T4 levels was also observed in the 2nd and 3rd trimesters (averages 1st: 1.15; 2nd: 0.99; 3rd: 0.94 ng/dl). Thyroid autoimmunity defined as positive TPOAb occurred in 13.9% of our patients during pregnancy. No significant differences in TSH and free T4 medium values were found between patients with positive TPOAb and those without. However, a significantly higher proportion of pregnants had abnormal hormonal values throughout the trimesters. We conclude that thyroid function is affected by pregnancy with a tendency for decline as it progresses, a feature more easily observed in positive TPOAb group.

Detecção do hipotireoidismo subclínico em gestantes com diferentes idades gestacionais

“…No curso da gestação ocorre uma gradual diminuição dos títulos de anticorpos anti-TPO, com elevação no puerpério. Estudos demonstram que a prevalência de anticorpos anti-tireoidianos nas gestantes variam de 1,9 a 18,7% (27)(28)(29). A presença de elevados títulos de anticorpos anti-TPO no primeiro trimestre da gestação aumentam a possibilidade de tireoidite pós-parto (TPP), e mulheres com anti-TPO positivo apresentam risco relativo de 20 a 80 para desenvolver a TPP (16,30).…”