Changes in circulating concentrations of inhibins A and pro-alpha C during first trimester medical termination of pregnancy.
BACKGROUND
Both inhibin A and inhibin pro-alpha C are detectable in the circulation in increasing amounts during establishment of pregnancy. However, their origins and functions remain to be elucidated. We have studied levels of inhibin A and inhibin pro-alpha C in serum samples collected at various stages during medical termination of pregnancy with consecutive use of mifepristone and misoprostol.


METHODS
Samples were collected from three groups of patients at different weeks of gestation (group A: 6-7 weeks, n = 6; group B: 7-8 weeks, n = 6; group C: 8-9 weeks, n = 6) at the time of administration of oral mifepristone, 48 h later just before administration of vaginal misoprostol and again soon after expulsion of the products of conception. Plasma concentrations of inhibin A and pro-alpha C were assayed using specific and sensitive enzyme-linked immunosorbent assays. Results were correlated with concentrations of hCG and progesterone.


RESULTS
We observed a significant fall in plasma concentration of inhibin pro-alpha C following administration of mifepristone, which continued after administration of misoprostol. In contrast mifepristone had no effect on plasma levels of inhibin A, which fell steeply only after administration of misoprostol.


CONCLUSIONS
These results suggest dissociation between major sources of inhibin A and inhibin pro-alpha C in early pregnancy. Treatment with mifepristone, a competitive antagonist of the progesterone receptor, resulted in a significant and rapid fall in concentrations of inhibin pro-alpha C, identifying a link between production of pro-alpha C and luteal steroidogenesis. In contrast, concentrations of inhibin A did not fall after mifepristone, identifying a predominantly feto-placental origin in early human pregnancy.
Lahiri
S
S
Academic Unit of Obstetrics and Gynaecology, University Department of Reproductive and Developmental Medicine, The Jessop Wing, Tree Root Walk, Sheffield S10 2SF, UK.
Anobile
C J
CJ
Stewart
P
P
Ledger
W L
WL
D000021:Abortifacient Agents, Steroidal / Q000008:administration & dosage; D000028:Abortion, Induced; D000282:Administration, Intravaginal; D000284:Administration, Oral; D006063:Chorionic Gonadotropin / Q000097:blood; D004334:Drug Administration Schedule; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006727:Hormone Antagonists / Q000008:administration & dosage; D006801:Humans; D007265:Inhibins / Q000097:blood*; D015735:Mifepristone / Q000008:administration & dosage; D009994:Osmolar Concentration; D011247:Pregnancy / Q000097:blood*; D011261:Pregnancy Trimester, First; D011374:Progesterone / Q000097:blood; D011498:Protein Precursors / Q000097:blood*
D000021:Abortifacient Agents, Steroidal; D006063:Chorionic Gonadotropin; D006727:Hormone Antagonists; D011498:Protein Precursors; C422362:inhibin A; C095971:inhibin-alpha subunit precursor; D015735:Mifepristone; D011374:Progesterone; D007265:Inhibins