Baird et al used urine measurement of ovarian hormone metabolites to determine a day of ovulation. Ovulation usually occurs within 24 hours of the peak in serum LH concentration. The authors are from the National Institute of Environmental Health Sciences at Research Triangle Park in North Carolina.
Specimen: first morning urine
Parameters:
(1) urine estrone-3-glucuronide (an estrogen metabolite indicating follicle hormone production) in ng per mg creatinine
(2) urine pregnanediol-3-glucuronide (a progresterone metabolite indicating luteal hormone production) in µg per mg creatinine
ratio =
= (urine estrone-3-glucuronide) / (urine pregnanediol-3-glucuronide)
Urine samples are tested daily for several days around mid-cycle.
The target interval (that encompasses ovulation) is defined as:
(1) the first 5 day period meeting criteria 2 and 3
(2) the ratio on the first day is maximum for the interval
(3) the ratio on days 4 and 5 are <= 40% of the day 1 values.
The second day of the target interval is designated the day of luteal transition.
Urine LH correlates with the serum concentration, so in theory the peak in urinary LH can identify the day of luteal transition. The authors found that the first morning urine specimen does not provide a consistent measure of the LH surge because it is often collected before the surge occurs. Perhaps a late morning sample would be better.
