Objective: To compare progesterone (P) and pregnanediol glucuronide (PDG) levels in urine with respect to their potential use for monitoring luteal activity and P treatment.
Study design: Two different experiments were carried out. In the first experiment, each of seven normal, ovulatory women collected first morning urines daily throughout an entire menstrual cycle. The day of ovulation was determined by transvaginal ultrasound scanning. P, PDG, estrone glucuronide, luteinizing hormone and creatinine were measured in each urine specimen. In the second experiment, each of three normal, ovulatory women was given a single oral dose of 200 mg of micronized P and, 2 days later, a single intramuscular injection of 25 mg of P during days 2-5 of the cycle. Blood and urine were collected prior to each treatment and 1, 4, 8, 12 and 24 hours after treatment. P was measured in both serum and urine; PDG was quantified only in urine.
Results: The mean initial rises and peak days, as well as the patterns of urinary excretion of P and PDG during the menstrual cycles, were similar; however, the variability of PDG was much greater. Concentrations of PDG were 1,000-4,000 times greater than those of P. A significant correlation was observed between urinary P and PDG. Following either intramuscular or oral P treatment, serum P levels rose rapidly and reached peak levels (7.0-11.8 ng/mL) by one hour. In contrast, both urinary P and PDG peaked considerably later (4-12 hours). Twenty-four hours after intramuscular treatment, serum and urinary P and urinary PDG were still elevated. Following oral treatment the levels of these compounds decreased after peaking and were 10- to 20- fold lower at 24 hours. Also, after oral P treatment, urinary PDG levels were considerably higher and more variable as compared to urinary P levels.
Conclusion: Urinary P appears to be as good a clinical marker of luteal activity and therapeutic P administration as PDG and may be measured in place of this metabolite. There appears to be greater variability in urinary PDG as compared to urinary P when P is administered.