Comparison between creatinine and pregnanediol adjustments in the retrospective analysis of urinary hormone profiles during the human menstrual cycle

Measurement of reproductive hormones in urine is a practical way of obtaining large amounts of information; however, there is still controversy on how to overcome problems derived from volume fluctuations between samples. Creatinine adjustment is a widely accepted solution, however, it introduces an extra cost, and large studies involving multiple sequential determinations would benefit from more economical solutions. We determined the value of creatinine adjustment, and compared it with a mathematical method that uses the smoothed profile of pregnanediol (PdG) as a reference to adjust other hormonal markers. To do this, we investigated the effects on three major urinary reproductive hormonal markers (luteinizing hormone (LH), estrone 3-glucuronide (E1G) and PdG) in 17 complete menstrual cycles. Detection of the day of LH peak did not differ between raw and adjusted data. Creatinine adjustment reduced variation in preovulatory E1G levels between individuals, though the effect was negligible within individuals. No significant differences were found regarding postovulatory PdG rise. Although creatinine adjustment significantly reduces variability, producing smoother profiles, an equivalent degree of smoothness is obtained using the PdG adjustment. We conclude that under the current technology, for the retrospective study of urinary hormonal profiles in the human menstrual cycle, PdG adjustment is a valid alternative to creatinine.