The present study was undertaken to evaluate thyroid function and thyrotropic action
of hCG in multiple pregnancy. We examined serum samples from 9 multiple pregnant women
(3 triplets and 6 twins) and 27 singleton pregnant women as control subjects. Serum
hCG levels in multiple pregnancy were higher than those in singleton pregnancy in
the second and third trimesters (P < 0.01). The mean free T3 and T4 concentrations
in multiple pregnancy did not differ from those in singleton pregnancy in each trimester.
Serum hCG levels showed a statistically significant positive correlation with free
T3 and T4 levels in singleton pregnancy (P < 0.001). However, these correlations were
not observed in multiple pregnancy. Thyroid stimulation activity (TSA) determined
by cAMP accumulation in FRTL-5 cells in multiple pregnancy sera was significantly
higher than that in singleton pregnancy in the first trimester (P < 0.05), but did
not differ in the second and third trimesters. Moreover, TSA did not show any correlation
with serum hCG levels in multiple pregnancy in contrast with the results in normal
pregnancy. A bioactivity/immunoreactivity ratio of hCG in multiple pregnancy was lower
than in singleton pregnancy in the second and third trimesters. The discrepancy between
immunoreactivity and thyrotropic activity of hCG may be caused by the variable thyrotropic
potency of heterogeneous hCG molecules in multiple pregnancy.
Human Chorionic Gonadotropin - Thyrotropin - Thyroid Hormone - Multiple Pregnancy
- Hyperemesis
