Total and Free Thyroxine and Triiodothyronine in Normal and Complicated Pregnancy

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Abstract
Serum concentrations of total and free thyroxine (T4 and FT4) and total and free triiodothyronine (T3 and FT3) were measured in normal pregnant women, in patients with toxemia of pregnancy, and in patients with gestational trophoblastic disease (GTD). In normal pregnancy, FT4 and FT3 levels remained normal while T4 and T3 levels were elevated. In patients with pre-eclampsia, the mean serum T3 concentration was significantly lower than that of normal pregnancy and the serum FT3 concentrations in three out of nine patients were below the normal pregnancy range. The mean serum T4 and FT4 concentrations in patients with preeclampsia were, however, significantly higher than those in normal pregnant women. In patients with GTD without signs of hyperthyroidism, the mean serum total and free T4 concentrations were 43 and 92% higher than those in normal pregnancy (P < 0.02), and many patients had levels above the range of values observed in normal pregnant women. The mean serum total and free T3 concentrations in GTD patients without signs of hyperthyroidism were not different from those of normal pregnancy (P > 0.05). In the single GTD patient with hyperthyroid crisis, the serum FT4 concentration was within the range seen in GTD patients without signs of hyperthyroidism. Her serum FT3 concentration was, however, much higher than the ranges in normal pregnancy or in GTD patients without clinical hyperthyroidism. Higher than normal FT4 levels were found in patients with and without elevated hCG levels.