Serum relaxin and the major endometrial secretory proteins in in-vitro fertilization and down-regulated hormone-supported and natural cycle frozen embryo transfer.

Abstract

Relaxin has been postulated to be a modulator of the expression of the endometrial secretory proteins, insulin-like growth factor binding protein (IGFBP-1) and placental protein 14 (PP14). This study evaluated the expression of relaxin in relation to concentrations of these secretory proteins along with oestradiol, progesterone and human chorionic gonadotrophin in groups of pregnant and non-pregnant patients who underwent differing assisted conception treatments. Serum samples were taken from 88 patients at 8 and 12 days after embryo transfer. At 12 days after embryo transfer, relaxin concentrations in the pregnant patients who had undergone in-vitro fertilization (IVF) or natural cycle frozen embryo transfer were significantly higher than those who did not conceive in these groups (mean concentrations 8334 versus 28 and 2608 versus 62 pg/ml respectively, P<0.001). However concentrations in the pregnant patients who had hormone support and transfer of frozen embryos were not significantly different from the patients who did not conceive after the same treatment. Although relaxin expression was associated with corpus luteum activity, it was not related to the number of corpora lutea in IVF patients. A wide range of relaxin concentrations was seen to be compatible with a healthy pregnancy. These serum relaxin concentrations were not found to be directly related to the serum concentrations of IGFBP-1, PP14 or the other factors assessed in this study.