Definition: Steroids containing the fundamental tetracyclic unit with no methyl groups at C-10 and C-13 and with no side chain at C-17. The concept includes both saturated and unsaturated derivatives.
Arch Biochem Biophys 172(2):434;1976; Biomed Mass Spectrom 4(1):48;1977; Br J Cancer 1979;40(6):914; Br J Cancer 28(1):84;1973; Cancer Res 1979;39(10):4160; Cancer Res 36(12):4387;1976