title: Modulation of human chorionic gonadotrophin bioactivity during the first trimester of pregnancy.
abstract: The objective of this study was to evaluate the bioactivity of human chorionic gonadotrophin (HCG) during first trimester pregnancy. This was done by means of a retrospective analysis of sera from patients with first trimester normal intrauterine and ectopic pregnancies. Serum samples were obtained from 38 women with amenorrhoea of <10 weeks. From these, 19 had a normal intrauterine pregnancy (IUP) and 19 an ectopic pregnancy (EP). Cases were allocated to either low serum immunoreactive HCG (HCGi), intermediate HCGi or high HCGi concentrations (HCGi <5000 mUI/ml, between 5000 and 40,000 mIU/ml and >40,000 mIU/ml respectively). HCGi and oestradiol were measured by enzyme immunoassays and bioactive HCG by the mouse Leydig cell bioassay. All results were analysed by analysis of variance and unpaired Student's t-test. There was a significant difference between bioactive to immunoreactive HCG ratios (b/i ratio) between the subgroups of low, intermediate and high HCGi concentrations. Lower b/i ratios were found when HCGi concentrations were high (HCG b/i mean +/- SEM: high subgroup, 0.33 +/- 0.07 versus low subgroup: 1.50 +/- 0.12; P < 0.0001). Furthermore, the b/i ratios were inversely correlated with oestradiol (P < 0.0001) and HCGi (P < 0.0001) concentrations but not with gestational age. There was no difference in the b/i ratios when comparing IUP with EP. It is concluded that, in first trimester pregnancies, there is a likely modulation of HCG bioactivity which is inversely correlated with HCGi and oestradiol concentration. The underlying mechanisms and their physiological relevance remain to be elucidated.
authors.affiliation: Department of Obstetrics and Gynaecology, University Hospital, Geneva, Switzerland.
authors.forename: P
authors.initials: P
authors.lastname: Mock
authors.forename: P
authors.initials: P
authors.lastname: Bischof
authors.forename: R
authors.initials: R
authors.lastname: Rivest
authors.forename: A
authors.initials: A
authors.lastname: Campana
authors.forename: D
authors.initials: D
authors.lastname: Chardonnens
mesh_terms: D000818:Animals; D006063:Chorionic Gonadotropin / Q000097:blood*; D005260:Female; D006801:Humans; D007118:Immunoassay; D051379:Mice; D011247:Pregnancy; D011261:Pregnancy Trimester, First / Q000097:blood*
chemical_list: D006063:Chorionic Gonadotropin