Depressive disorder and thyroid axis functioning during pregnancy

Background. Depression and thyroid dysfunction are prevalent in women, including pregnant women. The aim of this study was to assess the relationship between depression and thyroid function during pregnancy. Methods. One hundred and ninety-nine pregnant women three times during pregnancy were assessed for depressive disorder and for thyroid stimulating hormone (TSH) and free thyroxine (FT4) concentrations. Results. Prevalence of depressive disorder was 6.5% in early pregnancy, 3.0% in middle pregnancy and 3.5% in late pregnancy. There were no women with overt thyroid dysfunction. Subclinical hyperthyroidism was found in 23% of women in early pregnancy, in 5% of women in middle pregnancy and in 6% of women in late of pregnancy. In late pregnancy depressed women compared to non-depressed women had significantly higher FT4 concentrations and a strong trend towards lower TSH concentrations as well as higher prevalence of subclinical hyperthyroidism. Conclusions. These findings show an association between thyroid dysfunction and depression in late pregnancy. Because gestational depression might interfere with pregnancy outcome, evaluation of thyroid function during gestation is warranted.