SOURCE OF CIRCULATING LEVELS OF INHIBIN-A, PRO-ALPHA-C-CONTAINING INHIBINS AND ACTIVIN-A IN EARLY-PREGNANCY

It is now established that the glycoprotein hormone inhibin is produce d by primate granulosa cells, corpus luteum and trophoblast of human p lacenta, This study was designed to investigate the major source of in hibins and activin A in early pregnancy using a novel panel of assays with high specificity and sensitivity. A total of 12 women (aged 20-35 years) with singleton pregnancy undergoing first trimester (group 1: 6-8; group 2: 8-10; group 3: 10-12 weeks of gestation) termination of pregnancy (TOP) was recruited for the study Blood samples were taken b efore TOP, every 15 min for the first hour and hourly for the next 3 h after TOP (total of 4 h of measurements), Circulating concentrations of inhibin A, pro alpha C, activin A, human chorionic gonadotrophin (H CG), oestradiol and progesterone were higher in early pregnancy than a t any stage of the menstrual cycle, Peripheral concentrations of inhib in A and activin A were significantly decreased within the first hour in all three groups and gradually decreased to even lower concentratio ns within the study period, Pro alpha C concentrations decreased withi n the first hour and then remained unaltered during the next 3 h, Simi larly, HCG, oestradiol and progesterone concentrations in circulation decreased substantially within 3 h of TOP, Correlation analyses showed a significant positive correlation (P < 0.001) between inhibin A, act ivin A, HCG, and oestradiol concentrations throughout the study period , In summary, this study shows that the fete-placental unit is the maj or source of increased circulating concentrations of inhibin A in earl y pregnancy, Activin A is produced by the fete-placental unit and the corpus luteum, Pro alpha C-containing inhibins are mainly secreted by the corpus luteum in early pregnancy.