Thyroid hormones in the human pregnancy.

Radio-immunologic T3, T4, FT3, FT4, rT3, TBG and 17 beta-estradiol were measured in women in the 2nd and 3rd trimester of pregnancy, during labor, and during the first 14 days of the puerperium. A group of women suffering with gestosis EPH were also investigated. Our data suggest that in women suffering with gestosis EPH and during labor in normal pregnancy there is a T3-selective defect (low T3 syndrome) in which the conversion route of T4 into T3 is inhibited while the conversion route of T4 into rT3 remains fully operative, resulting in low plasma levels of T3 and FT3 and normal levels of T4, normal or high levels of FT4 and high levels of reverse T3.