Increases in Serum Thyroxin during Uncomplicated Pregnancy.

Abstract

89 sera obtained from 57 pregnant women usually during the 2d or 3d trimester were analyzed in duplicate or triplicate for protein-bound iodine (PBI) concn., 23 of these were also analyzed for thyroxin. The mean PBI value was found to be 7.8 [plus or minus] 1.3 [mu]g.%, compared to the avg. of 5.4 [plus or minus] 0.7 obtained in 81 sera from 25 non-pregnant, euthyroid adults. Similarly the thyroxin moiety of the PBI was found to be significantly increased with a mean of 5.4 [plus or minus] 1 as compared to 3.7 [plus or minus] 0.8 [mu]g.% in 23 control subjects. These findings confirm published reports that uncomplicated pregnancy in the human is frequently associated with a rise in circulating PBI and establish that the thyroxin portion of the PBI is also increased.