Total and free serum thyroid hormone concentrations in fetal and adult pregnant and nonpregnant XXXX .

@entity1 @entity742 @entity840 @entity95 @entity3938 @entity35
Information on total and free serum thyroid hormone concentrations in the adult and fetal @entity840 ( @entity840 ) is limited. These variables were studied in adult male and female @entity840 and in pregnant @entity840 and their fetuses at various times during gestation. Total serum T4 levels in adult males, nonpregnant females, and pregnant females did not differ significantly [range, 2.5 +/- 0.3 to 3.2 +/- 0.8 micrograms/dl (mean +/- SD)]. Similarly, there were no significant differences in the percent free T4 (0.046-0.068%), free T4 (1.26-2.03 ng/dl), total @entity3938 (39-44 ng/dl), the percent free @entity3938 (0.521-0.638%), and free @entity3938 (0.221-0.260 ng/dl) among adult males, nonpregnant females, and pregnant females. @entity3938 was undetectable in adult male, nonpregnant female, and pregnant female guinea pig serum. T4 values were similar and those for @entity3938 were lower in fetal compared to maternal serum at 45 days of gestation, whereas serum @entity3938 was detectable in fetal serum. Between 45 and 62 days of gestation, fetal serum T4 increased from 2.5 to 0.3 to 4.3 +/- 1.3 micrograms/dl (mean +/- SD, P less than 0.01), fetal serum @entity3938 remained unchanged, and fetal serum @entity3938 increased from 5.2 +/- 3.3 to 25.0 +/- 11.4 ng/dl (P less than 0.01). Near term, fetal serum total and free T4 and total @entity3938 concentrations were significantly higher and total and free @entity3938 concentrations were significantly lower than the corresponding values in maternal serum. Total serum T4 is higher in the @entity840 than in the @entity95 , is similar to values in the @entity35 , and is lower than values in @entity1 . The free T4 concentration in guinea pig serum is similar to those in @entity1 and @entity35 . The ontogenesis of thyroid hormones differs strikingly in the @entity840 fetus compared to that in the @entity35 fetus and shares many similarities with @entity742 and @entity1 fetal thyroid development.
