Endometrial inhibin/activin beta-B subunit expression is related to decidualization and is reduced in tubal ectopic pregnancy

J Clin Endocrinol Metab. 2008 Jun;93(6):2375-82. doi: 10.1210/jc.2008-0136. Epub 2008 Apr 1.


Context: Ectopic pregnancy is common but remains difficult to diagnose accurately. There is no serum test to differentiate ectopic from intrauterine gestation.

Objective: Our objective was to investigate differential gene expression in decidualized endometrium of ectopic pregnancy.

Design: Tissue and serum analysis informed by microarray study was performed.

Setting: The study was performed at a large United Kingdom teaching hospital.

Patients or other participants: Women undergoing surgical termination of pregnancy (n = 8), evacuation of uterus for miscarriage (n = 6), and surgery for tubal ectopic pregnancy (n = 11) were included in the study. Endometrium was collected from normally cycling women undergoing hysterectomy.

Interventions: Decidualized endometrium was subjected to microarray analysis, morphological assessment, and immunohistochemistry. Endometrial stromal fibroblasts were cultured in the presence of decidualizing stimuli.

Main outcome measures: Differential expression of potentially secreted molecules was calculated.

Results: Inhibin/activin beta-B expression was lower in decidualized endometrium from ectopic pregnancies when compared with that of ongoing pregnancies (P < 0.01) or miscarriages (P < 0.01). The localization of the beta-B subunit was more marked in decidualized than nondecidualized stroma. Decidualization of stromal fibroblasts in vitro was associated with increased beta-B expression (P < 0.05). Endometrial stroma of ectopic pregnancies was less decidualized morphologically (P < 0.05), with lower prolactin (P < 0.01) and IGF binding protein-1 (P < 0.005) expression. Serum activin B was lower in ectopic pregnancies (P < 0.005) than in intrauterine pregnancies, whereas there was no difference in progesterone concentrations.

Conclusions: Despite similar concentrations of progesterone, the endometrium of ectopic pregnancies is less decidualized than intrauterine pregnancies. Expression of the beta-B subunit is related to decidualization and can be detected in the circulation as activin B. Serum activin B concentrations are lower in ectopic pregnancy.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Abortion, Spontaneous / genetics
  • Abortion, Spontaneous / metabolism
  • Adolescent
  • Adult
  • Cells, Cultured
  • Decidua / metabolism
  • Down-Regulation
  • Embryo Implantation / genetics
  • Embryo Implantation / physiology*
  • Endometrium / metabolism*
  • Female
  • Gene Expression Profiling
  • Humans
  • Inhibin-beta Subunits / blood
  • Inhibin-beta Subunits / genetics*
  • Inhibin-beta Subunits / metabolism
  • Middle Aged
  • Oligonucleotide Array Sequence Analysis
  • Pregnancy
  • Pregnancy, Tubal / blood
  • Pregnancy, Tubal / genetics*
  • Pregnancy, Tubal / metabolism
  • Protein Subunits / genetics
  • Protein Subunits / metabolism
  • Tissue Distribution


  • INHBB protein, human
  • Protein Subunits
  • Inhibin-beta Subunits