Serum Thyroxine & Triiodothyronine Levels in Normal Pregnancy and Pre-Eclampsia

Abstract

To evaluate the thyroid hormone levels in pre-eclampsia and normal pregnancy, a study was undertaken among 54 women of age ranged from 18 to 35 years without present or past history of thyroid diseases. Among the study subjects, 32 women were patients of pre-eclampsia, 12 women were in their normal third trimester pregnancy and 10 women were married but nonpregnant (without having hormonal contraceptives at least for 6 months). We have measured serum levels of total and free thyroxine (TT₄ & FT₄) and total and free triiodothyronine (TT₃ & FT₃) by using RIA. The mean serum TT₄ and TT₃ in normal pregnancy were significantly higher compared to that of non-pregnant women when mean FT₄ and FT₃ were similar in both normal pregnancy and non-pregnant women. In pre-eclampsia, mean serum TT₄ and TT₃ were significantly higher than that of non-pregnant women but compared to that of normal pregnancy, TT₄ was clearly higher but not significant when TT₃ was significantly lower. The mean serum FT₄ was significantly higher in pre-eclampsia compared to non-pregnant women and not significantly higher compared to normal pregnancy. The mean serum FT₃ was similar in both non-pregnant and normal pregnancy but significantly lower in pre-eclampsia compared to normal pregnancy. In pregnancy i.e. in both normal pregnancy and pregnancy with preeclampsia, the increased serum thyroid hormone levels might result from increased stimulatory effect of placental hormones (hCG), increased metabolic demands in pregnancy and mental stress in pregnancy as mentioned by other investigators. Decreased TT₃ and FT₃ associated with higher TT₄ in pre-eclampsia might be due to reduced conversion of T₄ to T₃ in the liver and kidneys.  

doi: 10.3329/taj.v20i1.3082

TAJ 2007; 20(1): 06-10