Hormonal Characteristics in the Early Luteal Phase of Conceptive and Nonconceptive Menstrual Cycles

Abstract

To determine whether serum hormone profiles are different in nonconceptive and conceptive menstrual cycles after ovulation and before implantation. Daily blood samples obtained during the luteal phase of nonconceptive cycles (n = 31) and conceptive cycles (n = 19) were analyzed (intersubject comparison). Samples obtained in sequential nonconceptive and conceptive cycles from five subjects (intrasubject comparisons) were analyzed to confirm results obtained with intersubject analysis. Serum luteinizing hormone (LH), follicle-stimulating hormone (FSH), estradiol (E(2)), progesterone, and relaxin were measured by immunoassay. A cell-based bioassay was used to determine whether the measurement of serum immunoreactive LH is a result of cross-reaction with human chorionic gonadotropin (hCG). Intersubject analysis showed that mean serum LH levels were significantly higher in conceptive cycles on day 4 and day 5 after the FSH peak in urine, and this was confirmed by intrasubject analysis. The addition of antibodies that precipitate hCG did not affect the activity of LH receptor ligand molecules in serum samples collected during the early luteal phase of conceptive cycles, as measured by bioassay. In contrast, this LH receptor binding activity was completely removed when precipitating antibodies for LH were added. The mean levels of serum E(2) were higher in conceptive cycles after day 4 following the FSH peak in urine. The mean values of serum FSH, progesterone, and relaxin were not significantly different in nonconceptive and conceptive cycles during the same time interval. The differences in luteal phase hormones may reflect alterations in signaling in the hypothalamic-pituitary-ovarian axis that begin during the preovulatory period of nonconceptive cycles.