The lipid droplets in Leydig cells contain esterified cholesterol that is derived from circulating lipoproteins and locally synthesised cholesterol (Fig. 11.2). Following hydrolysis, free cholesterol moves to mitochondria where the side chain is cleaved to form pregnenolone, which, in turn, is converted to testosterone in the endoplasmic reticulum. The amount of Leydig cell testosterone is small since newly synthesised hormone diffuses promptly into the plasma.
