Identification and quantification of unconjugated neutral steroids in adrenal and liver tissue of early and mid-term human fetuses

In order to study further the metabolism of neutral steroids in human fetal adrenal and liver tissue the fractions of unconjugated neutral steroids isolated from these tissues were analyzed by gas-liquid chromatography and gas chromatography — mass spectrometry. In the adrenals, pregnenolone and 17-hydroxypregnenolone, but no corticoids, were detected. In the liver, pregnenolone, 3α-hydroxy-5β-pregnan-20-one, 5β-pregnane-3α, 20α-diol and 3β, 16α-dihydroxy-5β-pregnan-20-one were found. Thus, all the free steroids detected were C₂₁ compounds. From these results and those obtained earlier by the analysis of the sulfate-conjugated steroids present in these tissues it is concluded that in the fetal adrenals $\text{in situ}$ both sulfated and unconjugated steroids are actively metabolized. Regarding the liver it is obvious that the conjugated metabolites of progesterone are rapidly eliminated from this tissue. Here, pregnenolone is present both in the free and sulfate conjugated form, whereas its metabolites are found only as sulfate conjugates.