What are the structural components of steroids?

A steroid is a fused tetracyclic compound composed of three carbon cyclohexanes (A, B, C) and one carbocyclic ring (D). The six-carbon rings A, B, and C in natural steroid molecules have a chair conformation (cyclohexane structure), which is the most stable conformation (the only exception is that the A ring in the estrogen molecule is a planar conformation of the aromatic ring) . The glyph of the word "甾" visually expresses the common structural features of these compounds: three lines represent three branches, and the "field" represents four rings.