Identification of the LH surge by measuring intact and total immunoreactivity in urine for prediction of ovulation time.

OBJECTIVES: In our earlier study, we separated three different molecular forms of urinary LH-ir (U-LH-ir) by gel filtration and identified them by immunoassay in urine from regularly menstruating women on periovulatory days. U-LH-ir is composed of intact luteinizing hormone (LH), its free beta-subunit (LHß), and the core fragment of LHß (LHßcf), the latter two establishing the non-intact portion of LH-ir. The aim was to determine whether timing of ovulation can be improved by detecting different molecular forms of U-LH-ir in women of reproductive age. METHODS: We determined intact and total U-LH-ir in 14 regularly menstruating women on consecutive periovulatory days during the menstrual cycle. Non-intact LH-ir was calculated as the arithmetic difference between total and intact LH-ir. In addition, LH-ir was determined in both serum and urine from four of the women throughout the menstrual cycle. RESULTS: During the LH surge, U-LH-ir consisted mainly of intact LH and presented with an abrupt increase. Intact U-LH-ir dropped rapidly within 1 day after the surge, reaching baseline levels at the end of the luteal phase. In contrast, LHßcf in urine increased further 1 day after the surge. After this, most of the U-LH-ir consisted of LHßcf and it remained strongly elevated (over fivefold compared to intact LH) for the first 3 days after the LH surge, moderately elevated (over threefold) thereafter until day + 5, and mildly elevated until day + 7. CONCLUSIONS: Total and non-intact LH-ir are potential add-on characteristics which can be utilized in ovulation predictor kits to measure LH-ir in urine beyond the LH surge during a broader time frame, thereby paving the way for more precise prediction of the timing of ovulation than that obtained with currently available products.

Intact luteinizing hormone (LH), LHß, and LHß core fragment in urine of menstruating women.

OBJECTIVES: We examined different molecular forms of luteinizing hormone (LH) in urine samples taken during periovulatory days with the aim of revealing different forms of LH immunoreactivity (LH-ir) in normally menstruating women. METHODS: Serum and first-morning-voided urine serum samples were obtained from six healthy, 22 to 38 years old, regularly menstruating women during their periovulatory days based on their previous menstrual cycles. The day of the LH surge was determined on the basis of serum LH concentrations and confirmed by an at least two-fold increase in urinary concentrations of intact LH on consecutive days. Different molecular forms of LH-ir were identified by gel filtration of first-morning-voided urine samples obtained from regularly menstruating women on periovulatory days. RESULTS: Different forms of LH immunoreactivity (LH-ir) were distinguished as intact LH, its free beta-subunit (LHß), and the core fragment of LHß (LHßcf) according to their molecular sizes. The latter two are also called non-intact LH. Intact LH was the dominating form on the day before and on the day of LH surge while LHßcf was the major form of LH immunoreactivity after the LH surge for the following 5-7 days. LHß was detected on the day of the LH surge as well as on the following day. CONCLUSIONS: These results indicate that LH is degraded in the kidneys and excreted as LHß, and mainly as LHßcf for 7 days following the LH peak.