Substantial Urinary Concentrations of Material Resembling 13-CoreFragment of Chorionic Gonadotropin /3-Subunit in Mid-Menstrual Cycle

We measured the day-to-day variations in concentrations of p-core, luteinizing hormone (LH), and a-subunit in urine during the menstrual cycle. The a-subunit concentrations showed a pattern similar to that of the LH concentrations. p-Core-like material was increased during and up to 3 to 4 days after the surge in urine LH. The urine LH concen-tration was associated with the presence of a-core immu-noreactivity during the urine LH peak. Chromatography showed that, at the peak LH concentration and at 2 days after the LH peak, p-core immunoreactivity could be ac-counted for by the presence of a peptide of low molecular mass similar to the p-core molecule of I,CG, but probably originating from the degradation of LH. The prolonged excretion of gonadotropin metabolites in the midcycle must be considered when p-core is being assessed as