Thyroid associated components in serum during normal pregnancy

Abstract

Thyroxine-binding globulin (TBG), thyroxine-binding prealbumin (TBPA), thyroxine (T4), free T4, triiodothyronine (T3), and TSH were studied throughout apparently normal pregnancy in 290 cases grouped in 2 wk intervals. TBG increased to a plateau level reached in the 24th wk and was hereafter unchanged until term. T4 showed an increase until the 16th wk of pregnancy and leveled off to a constant level for the rest of the pregnancy. Free T4 declined to almost subnormal values for the non-pregnant state which was reached around the 20th wk of pregnancy. T3 showed a slight and definite increase in the beginning of pregnancy and leveled off to constant value after the 14th wk. TSH increased towards the end of pregnancy also showing its maximum during the last 4 wk. TBPA showed constant values throughout pregnancy. The results are discussed in view of the use of modern techniques and previously missing data in literature (TBPA).