3,3'-Diiodothyronine sulfate cross-reactive material (compound W) in human newborns

Thyrosulfoconjugation appears to facilitate fetal-to-maternal transfer of 3,3'-diiodothyronine-sulfate (T(2)S). Elevated maternal levels of T(2)S cross-reactive material (compound W) are found in humans, with higher levels found in venous cord blood than in arterial samples. These findings are consistent with the postulate that the placenta plays an essential role in compound W production.

Serum compound W levels were measured by a T(2)S-specific radioimmunoassay in 60 serum samples from newborns with hyperbilirubinemia, age 1-30 d. In addition, 59 maternal serum samples, from day 1 to day 7 after uneventful deliveries, were studied.

As compared with day 1, at day 5, the mean (±SE) compound W level fell to 43.5 ± 6.8% (decay half-life (t(1/2)) = 4.12 d) and to 33.7 ± 4.6% (decay t(1/2) = 2.82 d) in the newborn and maternal groups, respectively. In the mothers, the level continued to decline along the same slope through day 7. In the newborns, however, the mean compound W level entered a slower phase of decay after the fifth day with a decay t(1/2) = 10.9 d.

Compound W is cleared at similar rates in newborn and postpartum maternal sera. This is consistent with the postulate that compound W is produced in the placenta.