<p>ABSTRACT</p><p>A defect implantation process is the major reason for unexplained infertility. Estrogen andprogesterone are steroid hormones preparing the endometrium for implantation. They mediatetheir effect through their receptors: estrogen receptor alpha and beta and progesteronereceptor A and B, respectively. Leukemia inhibitory factor (LIF), which is also important forimplantation, mediates its effect through LIF receptor and the coreceptor, gp130, and is downregulated by suppressors of cytokine signaling 1. The aim of the study was to compare thelevels of the steroid hormone receptors and LIF related factors in the endometrium of twogroups of women with the diagnosis unexplained infertility: one that became pregnant afterassisted reproduction and one that did not become pregnant. Before treatment of thesewomen, endometrial mRNA was collected during the window of implantation in themenstrual cycle. The levels of specific mRNAs were measured with real-time PCR. Womenwho had become pregnant had a significantly higher level of steroid hormone receptors. Thus,these proteins seem to be important for a pregnancy and may be suitable as receptivitymarkers.</p>

ABSTRACT A defect implantation process is the major reason for unexplained infertility. Estrogen andprogesterone are steroid hormones preparing the endometrium for implantation. They mediatetheir effect through their receptors: estrogen receptor alpha and beta and progesteronereceptor A and B, respectively. Leukemia inhibitory factor (LIF), which is also important forimplantation, mediates its effect through LIF receptor and the coreceptor, gp130, and is downregulated by suppressors of cytokine signaling 1. The aim of the study was to compare thelevels of the steroid hormone receptors and LIF related factors in the endometrium of twogroups of women with the diagnosis unexplained infertility: one that became pregnant afterassisted reproduction and one that did not become pregnant. Before treatment of thesewomen, endometrial mRNA was collected during the window of implantation in themenstrual cycle. The levels of specific mRNAs were measured with real-time PCR. Womenwho had become pregnant had a significantly higher level of steroid hormone receptors. Thus,these proteins seem to be important for a pregnancy and may be suitable as receptivitymarkers.