Metabolic clearance rate and production rate of 20 alpha-hydroxypregn-4-en-3-one in the menstrual cycle.

@article{Billiar1973MetabolicCR,
  title={Metabolic clearance rate and production rate of 20 alpha-hydroxypregn-4-en-3-one in the menstrual cycle.},
  author={Reinhart B. Billiar and T. J. Lin and Brian M. Little},
  journal={Gynecologic investigation},
  year={1973},
  volume={4 3},
  pages={
          148-54
        }
}
The metabolic clearance rate (MCRrB), plasma concentration, and production rate (PI) and conversion to progesterone of 20Α-hydroxypregn-4-en-3-one (20Α-OHP) have been determined in women during the menstrual cycle. The MCRrB was 3,110 ± 217 (SE) 1/day and was independent of the day of the cycle. The PI was 0.92–2.53 mg/day for days 6–18 of the cycle and 0.78–15.6 mg/day for days 20–24. The percent conversion of 20Α-OHP to progesterone was 4.88 ± 1.10 (SE)% and the calculated transfer constant… 
3 Citations
Changes in the blood concentrations of progesterone and 20 alpha-hydroxypregn-4-en-3-one during late pregnancy in the conscious rat: a specific role for metabolic clearance rate.
TLDR
Near term in the rat, the blood concentration of progesterone falls while that of 20 alpha-hydroxypregn-4-en-3-one (20 alpha-DHP) increases, but altered rates of hormone metabolism could also have a role.