E. Jauniaux et al., TOTAL AMOUNT OF CIRCULATING HUMAN CHORIONIC-GONADOTROPIN ALPHA-SUBUNIT AND BETA-SUBUNIT IN FIRST TRIMESTER TRISOMY-21 AND TRISOMY-18, Journal of Endocrinology, 148(1), 1996, pp. 27-31
The aim of this study was to evaluate the variations in the balance be
tween total (free and combined) circulating a and beta subunits of hum
an chorionic gonadotrophin (hCG) in trisomy 21 and 18. Maternal serum
samples were collected at 10 and 11 weeks of gestation from 22 singlet
on pregnancies with trisomy 21 (n=17) and trisomy 18 (n=5) and 66 chro
mesomally normal controls, matched for gestational age. The hCG and fr
ee alpha and beta subunits circulating levels were measured using spec
ific immunoradiometric assays and converted in a common unit system ob
tained using calibration of the assays with intact and thermally disso
ciated purified hCG preparation. In trisomy 21, the only significant d
ifference from controls was in the flee beta hCG level which was incre
ased. In trisomy 18, intact hCG, free beta hCG as well as total alpha
hCG and total beta hCG levels were significantly lower whereas the fre
e alpha hCG level was significantly higher than in controls. The decre
ase in total beta hCG was more pronounced than the decrease in total a
lpha hCG resulting in a significant increase in the total alpha- to be
ta hCG subunit ratio in trisomy 18. These findings suggest some modifi
cations in the biosynthesis and/or release rates of the hCG subunits i
n these trisomies.