The metabolic disposition of plasma 5 alpha-dihydroprogesterone (5 alpha-pregnane-3,20-dione) in women and men.

This study was conducted 1) to ascertain whether the high levels of plasma 5 alpha-dihydroprogesterone (5 alpha DHP) during the luteal phase of the human ovarian cycle and pregnancy are attributable to high rates of production or, alternatively, low rates of clearance, and 2) to estimate the relative distribution of the irreversible metabolism of 5 alpha DHP, i.e. hepatic compared with extrahepatic clearance of plasma 5 alpha DHP. The concentration of 5 alpha DHP in plasma of women during the luteal phase of the ovarian cycle and pregnancy is very high, viz. 12-40% that of progesterone. Thus, a potentially large source of steroid precursor is available for the formation of bioactive 5 alpha-pregnanolone metabolites. We found that the MCR of 5 alpha DHP in women and men is 4187 +/- 312 L plasma/24 h (range, 3181-5506; n = 6). The MCR of 5 alpha DHP as a function of body surface area was 2406 +/- 240 L/24 h.m2. The MCR of 5 alpha DHP, therefore, is the greatest of any steroid reported, except for that of th...