Monitoring the menstrual cycle: Comparison of urinary and serum reproductive hormones referenced to true ovulation

The aim of the study was to examine relationships and interindividual variations in urinary and serum reproductive hormone levels relative to ultrasound-observed ovulation in menstrual cycles of apparently normally menstruating women.

This was a prospective study of normally menstruating women (no known subfertility), aged 18-40 years (n = 40), who collected daily urine samples and attended the study centre for blood samples and transvaginal ultrasound during one complete menstrual cycle. Serum luteinising hormone (LH), progesterone, estradiol, urinary LH, pregnanediol-3- glucuronide (P3G) and estrone-3-glucuronide were measured. Ultrasound was conducted by two physicians and interpreted by central expert review.

Menstrual cycle length varied from 22 to 37 days (median 27 days). Ovulation by ultrasound ranged from day 8 to day 26 (median day 15). Serum and urinary hormone profiles showed excellent agreement. Estrogen and LH hormone peaks in urine and serum showed a range of signal characteristics across the study group before and after ovulation. The rise in estrogen and LH always occurred before ovulation; the progesterone rise from baseline always occurred after ovulation.

Urinary and serum reproductive hormones showed excellent agreement and may be used interchangeably. The beginning of the surge in serum and urinary LH was an excellent predictor of ovulation. The rise in progesterone and P3G above baseline was a consistent marker of luteinisation confirming ovulation. Both LH and progesterone surges delivered clear, sharp signals in all volunteers, allowing reliable detection and confirmation of ovulation.