Thyroid associated components in serum during normal pregnancy.

Thyroxine-binding globulin (TBG(, thyroxine-binding pre-albumin (TBPA), thyroxine (T4), free-T4, triiodothyronine (T3), and thyroid-stimulating hormone (TSH) were studied throughout apparently normal pregnancy in 290 cases grouped in 2 week intervals. TBG increased to a plateau level reached in the 24th week and was hereafter unchanged until term. T4 showed an increase until the 16th week of pregnancy and levelled off to a constant level for the rest of the pregnancy. Free-T4 declined to almost subnormal values for the non-pregnancy state which was reached around the 20th week of pregnancy. T3 showed a slight and definite increase in the beginning of pregnancy and levelled off to a constant value after the 14th week. TSH increased towards the end of pregnancy also showing its maximum during the last 4 weeks. 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).