THYROID FUNCTION IN HUMAN PREGNANCY .2. SERUM THYROXINE-BINDING PREALBUMIN (TBPA) AND THYROXINE-BINDING GLOBULIN (TBG) OF PREGNANT WOMEN AGED 14 THROUGH 43 YEARS

Although an estrogen-related increase in serum TBG is well known during normal pregnancy, gestational changes in binding capacity of the other major thyroxine-transport protein TBPA apparently are not established. Interrelations of serum TBPA, TBG, and BEI (butanol-extractable iodine) were compared at intervals during 122 normal pregnancies of women aged 14 to 43 years. In comparison with postpartum capacities, TBG of women aged 18 to 34 doubled by the eighteenth gestational week; capacities were not related to age; a mean of 56 ± 6.2 μg T4 per 100 ml. is proposed during 4 week intervals for women aged 14 to 17, 18 to 34, and 35 to 43 years. A total of 373 gestational TBPA capacities were significantly lower than 68 postpartum capacities (p < 0.001). TBPA means during pregnancy were related to age and varied reciprocally with BEI: 14-year-old girls had the highest BEI and the lowest TBPA capacities during pregnancy or post partum. © 1969.