Changes in the binding capacity of thyroxine-binding globulin (TBC), of total thyroxine (T4), of the free thyroxine index (FT4-I) and of thyrotropin (TSH) during normal pregnancy and in hydatidiform mole

TBC-index and total serum thyroxine were measured in 100 healthy nonpregnant and in 163 pregnant women during the 8. and 41. weeks of gestation. The free thyroxine index was calculated. The TBC-index was found to be elevated in pregnant women and rose continously with duration of pregnancy. The amount of total serum thyroxine was greater in pregnant women (p less than 0,01) without difference between early and late pregnancy. The free thyroxine index decreased continously during pregnancy (p less than 0,01). Serum TSH level were elevated during the first two trimesters of pregnancy. At the third trimester the TSH level were found within the normal range. In patients with hydatidiform mole TSH, total thyroxine, FT4-index, ETR-index as well as TSH levels were increased.