Steroid production from plasma cholesterol. I. Conversion of plasma cholesterol to placental progesterone in humans.

TLDR: The data indicate that, in pregnancies without a functioning fetal adrenal, virtually all placental progesterone is derived from maternal plasma cholesterol.

Abstract: Cholesterol-7α-3H was administered via the antecubital vein to 2 mothers bearing term anencephalic fetuses, 8 and 3 days prior to delivery, respectively. Blood and urine samples were collected daily, as well as fetal blood, fetal liver and placenta at delivery. A corpus luteum was excised the day after delivery in one case. The specific activity (SA) of cholesterol was measured in all tissues. At delivery, the SA (dpm/μmole) of placental progesterone was equal to the SA of the corresponding free maternal plasma cholesterol and the SA of the urinary pregnanediol in both cases. Fetal cholesterol as well as placental cholesterol had a SA which was lower than placental progesterone. These data indicate that, in pregnancies without a functioning fetal adrenal, virtually all placental progesterone is derived from maternal plasma cholesterol.