Final answer:
Cholesterol is the common precursor for all adrenal steroids. It is mainly synthesized in the liver and serves as the starting point for the synthesis of various steroid hormones, including the adrenal steroids cortisol.
Step-by-step explanation:
The common precursor for all adrenal steroids is cholesterol. Cholesterol, which is mainly synthesized in the liver, serves as a precursor to many steroid hormones, including adrenal steroids. Adrenal steroids such as cortisol are derived from cholesterol, which undergoes a series of enzymatic reactions to form these hormones. Cholesterol is also the precursor to other steroid hormones such as testosterone, estradiol, and Vitamin D.