Total amount of circulating human chorionic gonadotrophin α and β subunits in first trimester trisomies 21 and 18

Abstract

Abstract The aim of this study was to evaluate the variations in the balance between total (free and combined) circulating α and β subunits of human chorionic gonadotrophin (hCG) in trisomy 21 and 18. Maternal serum samples were collected at 10 and 11 weeks of gestation from 22 singleton pregnancies with trisomy 21 (n=17) and trisomy 18 (n=5) and 66 chromosomally normal controls, matched for gestational age. The hCG and free α and β subunits circulating levels were measured using specific immunoradiometric assays and converted in a common unit system obtained using calibration of the assays with intact and thermally dissociated purified hCG preparation. In trisomy 21, the only significant difference from controls was in the free βhCG level which was increased. In trisomy 18, intact hCG, free βhCG as well as total αhCG and total βhCG levels were significantly lower whereas the free αhCG level was significantly higher than in controls. The decrease in total βhCG was more pronounced than the decrease in total αhCG resulting in a significant increase in the total α- to βhCG subunit ratio in trisomy 18. These findings suggest some modifications in the biosynthesis and/or release rates of the hCG subunits in these trisomies. Journal of Endocrinology (1996) 148, 27–31