Measuring human chorionic gonadotropin in the absence of implantation with use of highly sensitive urinary assays for intact β-core and free β epitopes

Objective: To determine if human chorionic gonadotropin (hCG) can be absorbed from the uterine cavity in the absence of an embryo. Design: Prospective study. Setting: University-based assisted reproduction program. Patient(s): Eight functionally agonadal patients (age range, 33-46 years) who were taking hormone replacement therapy so that they could receive donated oocytes. Intervention(s): Intrauterine instillation of 50 mu L of hCG (10,000 IU) during a mock cycle before an attempt at oocyte donation. Main Outcome Measure(s): Spot urine measurements of different hCG epitopes (intact beta, beta-core, and free beta) at timed intervals (12, 20, 44, and 68 hours after instillation). Result(s): All hCG epitopes were detected in the urine at the first sampling interval, and levels decreased in subsequent sampling intervals. Measurement of the serum hCG level confirmed that systemic absorption had occurred and that the urine measurements were not a result of specimen contamination through the cervix. Conclusion(s): hCG may be systemically absorbed into the blood through the uterine cavity, even in the absence of implantation, and its metabolites may be measured with use of highly sensitive urinary assays. (C) 1998 by American Society for Reproductive Medicine.